=item Functions for SCALARs or strings
X<scalar> X<string> X<character>
-C<chomp>, C<chop>, C<chr>, C<crypt>, C<hex>, C<index>, C<lc>, C<lcfirst>,
-C<length>, C<oct>, C<ord>, C<pack>, C<q//>, C<qq//>, C<reverse>,
+=for Pod::Functions =String
+
+C<chomp>, C<chop>, C<chr>, C<crypt>, C<fc>, C<hex>, C<index>, C<lc>,
+C<lcfirst>, C<length>, C<oct>, C<ord>, C<pack>, C<q//>, C<qq//>, C<reverse>,
C<rindex>, C<sprintf>, C<substr>, C<tr///>, C<uc>, C<ucfirst>, C<y///>
+C<fc> is available only if the C<"fc"> feature is enabled or if it is
+prefixed with C<CORE::>. The C<"fc"> feature is enabled automatically
+with a C<use v5.16> (or higher) declaration in the current scope.
+
+
=item Regular expressions and pattern matching
X<regular expression> X<regex> X<regexp>
-C<m//>, C<pos>, C<quotemeta>, C<s///>, C<split>, C<study>, C<qr//>
+=for Pod::Functions =Regexp
+
+C<m//>, C<pos>, C<qr//>, C<quotemeta>, C<s///>, C<split>, C<study>
=item Numeric functions
X<numeric> X<number> X<trigonometric> X<trigonometry>
+=for Pod::Functions =Math
+
C<abs>, C<atan2>, C<cos>, C<exp>, C<hex>, C<int>, C<log>, C<oct>, C<rand>,
C<sin>, C<sqrt>, C<srand>
=item Functions for real @ARRAYs
X<array>
+=for Pod::Functions =ARRAY
+
C<each>, C<keys>, C<pop>, C<push>, C<shift>, C<splice>, C<unshift>, C<values>
=item Functions for list data
X<list>
+=for Pod::Functions =LIST
+
C<grep>, C<join>, C<map>, C<qw//>, C<reverse>, C<sort>, C<unpack>
=item Functions for real %HASHes
X<hash>
+=for Pod::Functions =HASH
+
C<delete>, C<each>, C<exists>, C<keys>, C<values>
=item Input and output functions
X<I/O> X<input> X<output> X<dbm>
+=for Pod::Functions =I/O
+
C<binmode>, C<close>, C<closedir>, C<dbmclose>, C<dbmopen>, C<die>, C<eof>,
C<fileno>, C<flock>, C<format>, C<getc>, C<print>, C<printf>, C<read>,
-C<readdir>, C<rewinddir>, C<say>, C<seek>, C<seekdir>, C<select>, C<syscall>,
-C<sysread>, C<sysseek>, C<syswrite>, C<tell>, C<telldir>, C<truncate>,
-C<warn>, C<write>
+C<readdir>, C<readline> C<rewinddir>, C<say>, C<seek>, C<seekdir>, C<select>,
+C<syscall>, C<sysread>, C<sysseek>, C<syswrite>, C<tell>, C<telldir>,
+C<truncate>, C<warn>, C<write>
+
+C<say> is available only if the C<"say"> feature is enabled or if it is
+prefixed with C<CORE::>. The C<"say"> feature is enabled automatically
+with a C<use v5.10> (or higher) declaration in the current scope.
=item Functions for fixed-length data or records
-C<pack>, C<read>, C<syscall>, C<sysread>, C<syswrite>, C<unpack>, C<vec>
+=for Pod::Functions =Binary
+
+C<pack>, C<read>, C<syscall>, C<sysread>, C<sysseek>, C<syswrite>, C<unpack>,
+C<vec>
=item Functions for filehandles, files, or directories
X<file> X<filehandle> X<directory> X<pipe> X<link> X<symlink>
+=for Pod::Functions =File
+
C<-I<X>>, C<chdir>, C<chmod>, C<chown>, C<chroot>, C<fcntl>, C<glob>,
C<ioctl>, C<link>, C<lstat>, C<mkdir>, C<open>, C<opendir>,
C<readlink>, C<rename>, C<rmdir>, C<stat>, C<symlink>, C<sysopen>,
=item Keywords related to the control flow of your Perl program
X<control flow>
+=for Pod::Functions =Flow
+
C<caller>, C<continue>, C<die>, C<do>,
C<dump>, C<eval>, C<evalbytes> C<exit>,
C<__FILE__>, C<goto>, C<last>, C<__LINE__>, C<next>, C<__PACKAGE__>,
-C<redo>, C<return>, C<sub>, C<__SUB__>, C<wantarray>
+C<prototype>, C<redo>, C<return>, C<sub>, C<__SUB__>, C<wantarray>
-C<__SUB__> is only available with a C<use v5.16> (or higher) declaration or
-with the C<"current_sub"> feature (see L<feature>).
+C<evalbytes> is only available with with the C<"evalbytes"> feature (see
+L<feature>) or if prefixed with C<CORE::>. C<__SUB__> is only available
+with with the C<"current_sub"> feature or if prefixed with C<CORE::>. Both
+the C<"evalbytes"> and C<"current_sub"> features are enabled automatically
+with a C<use v5.16> (or higher) declaration in the current scope.
=item Keywords related to the switch feature
+=for Pod::Functions =Switch
+
C<break>, C<continue>, C<default>, C<given>, C<when>
Except for C<continue>, these are available only if you enable the
-C<"switch"> feature or use the C<CORE::> prefix.
-See L<feature> and L<perlsyn/"Switch statements">.
-Alternately, include a C<use v5.10> or later to the current scope. In Perl
-5.14 and earlier, C<continue> required the C<"switch"> feature, like the
-other keywords.
+C<"switch"> feature or use the C<CORE::> prefix. See L<feature> and
+L<perlsyn/"Switch Statements">. The C<"switch"> feature is enabled
+automatically with a C<use v5.10> (or higher) declaration in the current
+scope. In Perl 5.14 and earlier, C<continue> required the C<"switch">
+feature, like the other keywords.
=item Keywords related to scoping
+=for Pod::Functions =Namespace
+
C<caller>, C<import>, C<local>, C<my>, C<our>, C<package>, C<state>, C<use>
-C<state> is available only if the C<"state"> feature
-is enabled or if it is prefixed with C<CORE::>. See
-L<feature>. Alternately, include a C<use v5.10> or later to the current scope.
+C<state> is available only if the C<"state"> feature is enabled or if it is
+prefixed with C<CORE::>. The C<"state"> feature is enabled automatically
+with a C<use v5.10> (or higher) declaration in the current scope.
=item Miscellaneous functions
+=for Pod::Functions =Misc
+
C<defined>, C<dump>, C<eval>, C<evalbytes>,
-C<formline>, C<local>, C<my>, C<our>,
+C<formline>, C<local>, C<lock>, C<my>, C<our>, C<prototype>,
C<reset>, C<scalar>, C<state>, C<undef>, C<wantarray>
=item Functions for processes and process groups
X<process> X<pid> X<process id>
+=for Pod::Functions =Process
+
C<alarm>, C<exec>, C<fork>, C<getpgrp>, C<getppid>, C<getpriority>, C<kill>,
C<pipe>, C<qx//>, C<readpipe>, C<setpgrp>,
C<setpriority>, C<sleep>, C<system>,
=item Keywords related to Perl modules
X<module>
+=for Pod::Functions =Modules
+
C<do>, C<import>, C<no>, C<package>, C<require>, C<use>
=item Keywords related to classes and object-orientation
X<object> X<class> X<package>
+=for Pod::Functions =Objects
+
C<bless>, C<dbmclose>, C<dbmopen>, C<package>, C<ref>, C<tie>, C<tied>,
C<untie>, C<use>
=item Low-level socket functions
X<socket> X<sock>
+=for Pod::Functions =Socket
+
C<accept>, C<bind>, C<connect>, C<getpeername>, C<getsockname>,
C<getsockopt>, C<listen>, C<recv>, C<send>, C<setsockopt>, C<shutdown>,
C<socket>, C<socketpair>
=item System V interprocess communication functions
X<IPC> X<System V> X<semaphore> X<shared memory> X<memory> X<message>
+=for Pod::Functions =SysV
+
C<msgctl>, C<msgget>, C<msgrcv>, C<msgsnd>, C<semctl>, C<semget>, C<semop>,
C<shmctl>, C<shmget>, C<shmread>, C<shmwrite>
=item Fetching user and group info
X<user> X<group> X<password> X<uid> X<gid> X<passwd> X</etc/passwd>
+=for Pod::Functions =User
+
C<endgrent>, C<endhostent>, C<endnetent>, C<endpwent>, C<getgrent>,
C<getgrgid>, C<getgrnam>, C<getlogin>, C<getpwent>, C<getpwnam>,
C<getpwuid>, C<setgrent>, C<setpwent>
=item Fetching network info
X<network> X<protocol> X<host> X<hostname> X<IP> X<address> X<service>
+=for Pod::Functions =Network
+
C<endprotoent>, C<endservent>, C<gethostbyaddr>, C<gethostbyname>,
C<gethostent>, C<getnetbyaddr>, C<getnetbyname>, C<getnetent>,
C<getprotobyname>, C<getprotobynumber>, C<getprotoent>,
=item Time-related functions
X<time> X<date>
-C<gmtime>, C<localtime>, C<time>, C<times>
-
-=item Functions new in perl5
-X<perl5>
+=for Pod::Functions =Time
-C<abs>, C<bless>, C<break>, C<chomp>, C<chr>, C<continue>, C<default>,
-C<exists>, C<formline>, C<given>, C<glob>, C<import>, C<lc>, C<lcfirst>,
-C<lock>, C<map>, C<my>, C<no>, C<our>, C<prototype>, C<qr//>, C<qw//>, C<qx//>,
-C<readline>, C<readpipe>, C<ref>, C<sub>*, C<sysopen>, C<tie>, C<tied>, C<uc>,
-C<ucfirst>, C<untie>, C<use>, C<when>
+C<gmtime>, C<localtime>, C<time>, C<times>
-* C<sub> was a keyword in Perl 4, but in Perl 5 it is an
-operator, which can be used in expressions.
+=item Non-function keywords
-=item Functions obsoleted in perl5
+=for Pod::Functions =!Non-functions
-C<dbmclose>, C<dbmopen>
+C<and>, C<AUTOLOAD>, C<BEGIN>, C<CHECK>, C<cmp>, C<CORE>, C<__DATA__>,
+C<DESTROY>, C<else>, C<elseif>, C<elsif>, C<END>, C<__END__>, C<eq>, C<for>,
+C<foreach>, C<ge>, C<gt>, C<if>, C<INIT>, C<le>, C<lt>, C<ne>, C<not>, C<or>,
+C<UNITCHECK>, C<unless>, C<until>, C<while>, C<x>, C<xor>
=back
=item -X
+=for Pod::Functions a file test (-r, -x, etc)
+
A file test, where X is one of the letters listed below. This unary
operator takes one argument, either a filename, a filehandle, or a dirhandle,
and tests the associated file to see if something is true about it. If the
access(2) family of system calls. Also note that the C<-x> and C<-X> may
under this pragma return true even if there are no execute permission
bits set (nor any extra execute permission ACLs). This strangeness is
-due to the underlying system calls' definitions. Note also that, due to
+due to the underlying system calls' definitions. Note also that, due to
the implementation of C<use filetest 'access'>, the C<_> special
filehandle won't cache the results of the file tests when this pragma is
in effect. Read the documentation for the C<filetest> pragma for more
As of Perl 5.9.1, as a form of purely syntactic sugar, you can stack file
test operators, in a way that C<-f -w -x $file> is equivalent to
-C<-x $file && -w _ && -f _>. (This is only fancy fancy: if you use
+C<-x $file && -w _ && -f _>. (This is only fancy fancy: if you use
the return value of C<-f $file> as an argument to another filetest
operator, no special magic will happen.)
Portability issues: L<perlport/-X>.
+To avoid confusing would-be users of your code with mysterious
+syntax errors, put something like this at the top of your script:
+
+ use 5.010; # so filetest ops can stack
+
=item abs VALUE
X<abs> X<absolute>
=item abs
+=for Pod::Functions absolute value function
+
Returns the absolute value of its argument.
If VALUE is omitted, uses C<$_>.
=item accept NEWSOCKET,GENERICSOCKET
X<accept>
+=for Pod::Functions accept an incoming socket connect
+
Accepts an incoming socket connect, just as accept(2)
does. Returns the packed address if it succeeded, false otherwise.
See the example in L<perlipc/"Sockets: Client/Server Communication">.
=item alarm
+=for Pod::Functions schedule a SIGALRM
+
Arranges to have a SIGALRM delivered to this process after the
specified number of wallclock seconds has elapsed. If SECONDS is not
-specified, the value stored in C<$_> is used. (On some machines,
+specified, the value stored in C<$_> is used. (On some machines,
unfortunately, the elapsed time may be up to one second less or more
than you specified because of how seconds are counted, and process
scheduling may delay the delivery of the signal even further.)
distribution) provides ualarm(). You may also use Perl's four-argument
version of select() leaving the first three arguments undefined, or you
might be able to use the C<syscall> interface to access setitimer(2) if
-your system supports it. See L<perlfaq8> for details.
+your system supports it.
See L<perlfaq8> for details.
It is usually a mistake to intermix C<alarm> and C<sleep> calls, because
C<sleep> may be internally implemented on your system with C<alarm>.
=item atan2 Y,X
X<atan2> X<arctangent> X<tan> X<tangent>
+=for Pod::Functions arctangent of Y/X in the range -PI to PI
+
Returns the arctangent of Y/X in the range -PI to PI.
For the tangent operation, you may use the C<Math::Trig::tan>
=item bind SOCKET,NAME
X<bind>
+=for Pod::Functions binds an address to a socket
+
Binds a network address to a socket, just as bind(2)
does. Returns true if it succeeded, false otherwise. NAME should be a
packed address of the appropriate type for the socket. See the examples in
=item binmode FILEHANDLE
+=for Pod::Functions prepare binary files for I/O
+
Arranges for FILEHANDLE to be read or written in "binary" or "text"
mode on systems where the run-time libraries distinguish between
binary and text files. If FILEHANDLE is an expression, the value is
like images, for example.
If LAYER is present it is a single string, but may contain multiple
-directives. The directives alter the behaviour of the filehandle.
+directives. The directives alter the behaviour of the filehandle.
When LAYER is present, using binmode on a text file makes sense.
If LAYER is omitted or specified as C<:raw> the filehandle is made
-suitable for passing binary data. This includes turning off possible CRLF
+suitable for passing binary data. This includes turning off possible CRLF
translation and marking it as bytes (as opposed to Unicode characters).
Note that, despite what may be implied in I<"Programming Perl"> (the
Camel, 3rd edition) or elsewhere, C<:raw> is I<not> simply the inverse of C<:crlf>.
Other layers that would affect the binary nature of the stream are
-I<also> disabled. See L<PerlIO>, L<perlrun>, and the discussion about the
+I<also> disabled.
See L<PerlIO>, L<perlrun>, and the discussion about the
PERLIO environment variable.
The C<:bytes>, C<:crlf>, C<:utf8>, and any other directives of the
To mark FILEHANDLE as UTF-8, use C<:utf8> or C<:encoding(UTF-8)>.
C<:utf8> just marks the data as UTF-8 without further checking,
while C<:encoding(UTF-8)> checks the data for actually being valid
-UTF-8. More details can be found in L<PerlIO::encoding>.
+UTF-8.
More details can be found in L<PerlIO::encoding>.
In general, binmode() should be called after open() but before any I/O
is done on the filehandle. Calling binmode() normally flushes any
All variants of Unix, Mac OS (old and new), and Stream_LF files on VMS use
a single character to end each line in the external representation of text
(even though that single character is CARRIAGE RETURN on old, pre-Darwin
-flavors of Mac OS, and is LINE FEED on Unix and most VMS files). In other
+flavors of Mac OS, and is LINE FEED on Unix and most VMS files). In other
systems like OS/2, DOS, and the various flavors of MS-Windows, your program
sees a C<\n> as a simple C<\cJ>, but what's stored in text files are the
two characters C<\cM\cJ>. That means that if you don't use binmode() on
=item bless REF
+=for Pod::Functions create an object
+
This function tells the thingy referenced by REF that it is now an object
in the CLASSNAME package. If CLASSNAME is omitted, the current package
is used. Because a C<bless> is often the last thing in a constructor,
Consider always blessing objects in CLASSNAMEs that are mixed case.
Namespaces with all lowercase names are considered reserved for
-Perl pragmata. Builtin types have all uppercase names. To prevent
+Perl pragmata. Builtin types have all uppercase names. To prevent
confusion, you may wish to avoid such package names as well. Make sure
that CLASSNAME is a true value.
=item break
+=for Pod::Functions +switch break out of a C<given> block
+
Break out of a C<given()> block.
This keyword is enabled by the C<"switch"> feature: see
=item caller
+=for Pod::Functions get context of the current subroutine call
+
Returns the context of the current subroutine call. In scalar context,
returns the caller's package name if there I<is> a caller (that is, if
we're in a subroutine or C<eval> or C<require>) and the undefined value
between versions of Perl, and are not meant for external use.
C<$hinthash> is a reference to a hash containing the value of C<%^H> when the
-caller was compiled, or C<undef> if C<%^H> was empty. Do not modify the values
+caller was compiled, or C<undef> if C<%^H> was empty. Do not modify the values
of this hash, as they are the actual values stored in the optree.
-Furthermore, when called from within the DB package, caller returns more
+Furthermore, when called from within the DB package in
+list context, and with an argument, caller returns more
detailed information: it sets the list variable C<@DB::args> to be the
arguments with which the subroutine was invoked.
previous time C<caller> was called.
Be aware that setting C<@DB::args> is I<best effort>, intended for
-debugging or generating backtraces, and should not be relied upon. In
+debugging or generating backtraces, and should not be relied upon. In
particular, as C<@_> contains aliases to the caller's arguments, Perl does
not take a copy of C<@_>, so C<@DB::args> will contain modifications the
subroutine makes to C<@_> or its contents, not the original values at call
-time. C<@DB::args>, like C<@_>, does not hold explicit references to its
+time. C<@DB::args>, like C<@_>, does not hold explicit references to its
elements, so under certain cases its elements may have become freed and
-reallocated for other variables or temporary values. Finally, a side effect
+reallocated for other variables or temporary values. Finally, a side effect
of the current implementation is that the effects of C<shift @_> can
I<normally> be undone (but not C<pop @_> or other splicing, I<and> not if a
reference to C<@_> has been taken, I<and> subject to the caveat about reallocated
elements), so C<@DB::args> is actually a hybrid of the current state and
-initial state of C<@_>. Buyer beware.
+initial state of C<@_>. Buyer beware.
=item chdir EXPR
X<chdir>
=item chdir
-Changes the working directory to EXPR, if possible. If EXPR is omitted,
+=for Pod::Functions change your current working directory
+
+Changes the working directory to EXPR, if possible. If EXPR is omitted,
changes to the directory specified by C<$ENV{HOME}>, if set; if not,
-changes to the directory specified by C<$ENV{LOGDIR}>. (Under VMS, the
-variable C<$ENV{SYS$LOGIN}> is also checked, and used if it is set.) If
-neither is set, C<chdir> does nothing. It returns true on success,
-false otherwise. See the example under C<die>.
+changes to the directory specified by C<$ENV{LOGDIR}>. (Under VMS, the
+variable C<$ENV{SYS$LOGIN}> is also checked, and used if it is set.) If
+neither is set, C<chdir> does nothing. It returns true on success,
+false otherwise. See the example under C<die>.
On systems that support fchdir(2), you may pass a filehandle or
directory handle as the argument. On systems that don't support fchdir(2),
=item chmod LIST
X<chmod> X<permission> X<mode>
+=for Pod::Functions changes the permissions on a list of files
+
Changes the permissions of a list of files. The first element of the
list must be the numeric mode, which should probably be an octal
number, and which definitely should I<not> be a string of octal digits:
=item chomp
+=for Pod::Functions remove a trailing record separator from a string
+
This safer version of L</chop> removes any trailing string
that corresponds to the current value of C<$/> (also known as
$INPUT_RECORD_SEPARATOR in the C<English> module). It returns the total
=item chop
+=for Pod::Functions remove the last character from a string
+
Chops off the last character of a string and returns the character
chopped. It is much more efficient than C<s/.$//s> because it neither
scans nor copies the string. If VARIABLE is omitted, chops C<$_>.
=item chown LIST
X<chown> X<owner> X<user> X<group>
+=for Pod::Functions change the ownership on a list of files
+
Changes the owner (and group) of a list of files. The first two
elements of the list must be the I<numeric> uid and gid, in that
order. A value of -1 in either position is interpreted by most
=item chr
+=for Pod::Functions get character this number represents
+
Returns the character represented by that NUMBER in the character set.
For example, C<chr(65)> is C<"A"> in either ASCII or Unicode, and
chr(0x263a) is a Unicode smiley face.
=item chroot
+=for Pod::Functions make directory new root for path lookups
+
This function works like the system call by the same name: it makes the
named directory the new root directory for all further pathnames that
begin with a C</> by your process and all its children. (It doesn't
=item close
+=for Pod::Functions close file (or pipe or socket) handle
+
Closes the file or pipe associated with the filehandle, flushes the IO
buffers, and closes the system file descriptor. Returns true if those
operations succeed and if no error was reported by any PerlIO
=item closedir DIRHANDLE
X<closedir>
+=for Pod::Functions close directory handle
+
Closes a directory opened by C<opendir> and returns the success of that
system call.
=item connect SOCKET,NAME
X<connect>
+=for Pod::Functions connect to a remote socket
+
Attempts to connect to a remote socket, just like connect(2).
Returns true if it succeeded, false otherwise. NAME should be a
packed address of the appropriate type for the socket. See the examples in
=item continue
+=for Pod::Functions optional trailing block in a while or foreach
+
When followed by a BLOCK, C<continue> is actually a
flow control statement rather than a function. If
there is a C<continue> BLOCK attached to a BLOCK (typically in a C<while> or
a dynamically enclosing C<foreach> or exiting a lexically enclosing C<given>.
In Perl 5.14 and earlier, this form of C<continue> was
only available when the C<"switch"> feature was enabled.
-See L<feature> and L<perlsyn/"Switch statements"> for more
+See L<feature> and L<perlsyn/"Switch Statements"> for more
information.
=item cos EXPR
=item cos
+=for Pod::Functions cosine function
+
Returns the cosine of EXPR (expressed in radians). If EXPR is omitted,
takes the cosine of C<$_>.
X<crypt> X<digest> X<hash> X<salt> X<plaintext> X<password>
X<decrypt> X<cryptography> X<passwd> X<encrypt>
+=for Pod::Functions one-way passwd-style encryption
+
Creates a digest string exactly like the crypt(3) function in the C
library (assuming that you actually have a version there that has not
been extirpated as a potential munition).
Traditionally the result is a string of 13 bytes: two first bytes of
the salt, followed by 11 bytes from the set C<[./0-9A-Za-z]>, and only
-the first eight bytes of PLAINTEXT mattered. But alternative
+the first eight bytes of PLAINTEXT mattered. But alternative
hashing schemes (like MD5), higher level security schemes (like C2),
and implementations on non-Unix platforms may produce different
strings.
=item dbmclose HASH
X<dbmclose>
+=for Pod::Functions breaks binding on a tied dbm file
+
[This function has been largely superseded by the C<untie> function.]
Breaks the binding between a DBM file and a hash.
=item dbmopen HASH,DBNAME,MASK
X<dbmopen> X<dbm> X<ndbm> X<sdbm> X<gdbm>
+=for Pod::Functions create binding on a tied dbm file
+
[This function has been largely superseded by the
L<tie|/tie VARIABLE,CLASSNAME,LIST> function.]
argument is I<not> a filehandle, even though it looks like one). DBNAME
is the name of the database (without the F<.dir> or F<.pag> extension if
any). If the database does not exist, it is created with protection
-specified by MASK (as modified by the C<umask>). If your system supports
+specified by MASK (as modified by the C<umask>). To prevent creation of
+the database if it doesn't exist, you may specify a MODE
+of 0, and the function will return a false value if it
+can't find an existing database. If your system supports
only the older DBM functions, you may make only one C<dbmopen> call in your
program. In older versions of Perl, if your system had neither DBM nor
ndbm, calling C<dbmopen> produced a fatal error; it now falls back to
=item default BLOCK
+=for Pod::Functions !RT #108848
+
Within a C<foreach> or a C<given>, a C<default> BLOCK acts like a C<when>
that's always true. Only available after Perl 5.10, and only if the
C<switch> feature has been requested or if the keyword is prefixed with
=item defined
+=for Pod::Functions test whether a value, variable, or function is defined
+
Returns a Boolean value telling whether EXPR has a value other than
the undefined value C<undef>. If EXPR is not present, C<$_> is
checked.
=item delete EXPR
X<delete>
+=for Pod::Functions deletes a value from a hash
+
Given an expression that specifies an element or slice of a hash, C<delete>
deletes the specified elements from that hash so that exists() on that element
no longer returns true. Setting a hash element to the undefined value does
=item die LIST
X<die> X<throw> X<exception> X<raise> X<$@> X<abort>
-C<die> raises an exception. Inside an C<eval> the error message is stuffed
+=for Pod::Functions raise an exception or bail out
+
+C<die> raises an exception. Inside an C<eval> the error message is stuffed
into C<$@> and the C<eval> is terminated with the undefined value.
If the exception is outside of all enclosing C<eval>s, then the uncaught
-exception prints LIST to C<STDERR> and exits with a non-zero value. If you
+exception prints LIST to C<STDERR> and exits with a non-zero value. If you
need to exit the process with a specific exit code, see L</exit>.
Equivalent examples:
exit 255; # last resort
The intent is to squeeze as much possible information about the likely cause
-into the limited space of the system exit code. However, as C<$!> is the value
+into the limited space of the system exit
+code. However, as C<$!> is the value
of C's C<errno>, which can be set by any system call, this means that the value
of the exit code used by C<die> can be non-predictable, so should not be relied
upon, other than to be non-zero.
=item do BLOCK
X<do> X<block>
+=for Pod::Functions turn a BLOCK into a TERM
+
Not really a function. Returns the value of the last command in the
sequence of commands indicated by BLOCK. When modified by the C<while> or
C<until> loop modifier, executes the BLOCK once before testing the loop
-condition. (On other statements the loop modifiers test the conditional
+condition. (On other statements the loop modifiers test the conditional
first.)
C<do BLOCK> does I<not> count as a loop, so the loop control statements
=item dump
+=for Pod::Functions create an immediate core dump
+
This function causes an immediate core dump. See also the B<-u>
command-line switch in L<perlrun>, which does the same thing.
Primarily this is so that you can use the B<undump> program (not
resulting confusion by Perl.
This function is now largely obsolete, mostly because it's very hard to
-convert a core file into an executable. That's why you should now invoke
+convert a core file into an executable. That's why you should now invoke
it as C<CORE::dump()>, if you don't want to be warned against a possible
typo.
=item each EXPR
-When called in list context, returns a 2-element list consisting of the key
-and value for the next element of a hash, or the index and value for the
-next element of an array, so that you can iterate over it. When called in
-scalar context, returns only the key (not the value) in a hash, or the index
-in an array.
+=for Pod::Functions retrieve the next key/value pair from a hash
+
+When called on a hash in list context, returns a 2-element list
+consisting of the key and value for the next element of a hash. In Perl
+5.12 and later only, it will also return the index and value for the next
+element of an array so that you can iterate over it; older Perls consider
+this a syntax error. When called in scalar context, returns only the key
+(not the value) in a hash, or the index in an array.
Hash entries are returned in an apparently random order. The actual random
order is subject to change in future versions of Perl, but it is
After C<each> has returned all entries from the hash or array, the next
call to C<each> returns the empty list in list context and C<undef> in
-scalar context. The next call following that one restarts iteration. Each
-hash or array has its own internal iterator, accessed by C<each>, C<keys>,
-and C<values>. The iterator is implicitly reset when C<each> has reached
-the end as just described; it can be explicitly reset by calling C<keys> or
-C<values> on the hash or array. If you add or delete a hash's elements
-while iterating over it, entries may be skipped or duplicated--so don't do
-that. Exception: It is always safe to delete the item most recently
-returned by C<each()>, so the following code works properly:
+scalar context; the next call following I<that> one restarts iteration.
+Each hash or array has its own internal iterator, accessed by C<each>,
+C<keys>, and C<values>. The iterator is implicitly reset when C<each> has
+reached the end as just described; it can be explicitly reset by calling
+C<keys> or C<values> on the hash or array. If you add or delete a hash's
+elements while iterating over it, entries may be skipped or duplicated--so
+don't do that. Exception: In the current implementation, it is always safe
+to delete the item most recently returned by C<each()>, so the following
+code works properly:
while (($key, $value) = each %hash) {
print $key, "\n";
while (($key,$value) = each $hashref) { ... }
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious syntax errors, put this sort of thing at
+the top of your file to signal that your code will work I<only> on Perls of
+a recent vintage:
+
+ use 5.012; # so keys/values/each work on arrays
+ use 5.014; # so keys/values/each work on scalars (experimental)
+
See also C<keys>, C<values>, and C<sort>.
=item eof FILEHANDLE
=item eof
+=for Pod::Functions test a filehandle for its end
+
Returns 1 if the next read on FILEHANDLE will return end of file I<or> if
FILEHANDLE is not open. FILEHANDLE may be an expression whose value
gives the real filehandle. (Note that this function actually
=item eval
+=for Pod::Functions catch exceptions or compile and run code
+
In the first form, the return value of EXPR is parsed and executed as if it
were a little Perl program. The value of the expression (which is itself
determined within scalar context) is first parsed, and if there were no
in case 6.
Before Perl 5.14, the assignment to C<$@> occurred before restoration
-of localised variables, which means that for your code to run on older
+of localized variables, which means that for your code to run on older
versions, a temporary is required if you want to mask some but not all
errors:
=item evalbytes
+=for Pod::Functions +evalbytes similar to string eval, but intend to parse a bytestream
+
This function is like L</eval> with a string argument, except it always
parses its argument, or C<$_> if EXPR is omitted, as a string of bytes. A
string containing characters whose ordinal value exceeds 255 results in an
=item exec PROGRAM LIST
+=for Pod::Functions abandon this program to run another
+
The C<exec> function executes a system command I<and never returns>;
use C<system> instead of C<exec> if you want it to return. It fails and
returns false only if the command does not exist I<and> it is executed
=item exists EXPR
X<exists> X<autovivification>
+=for Pod::Functions test whether a hash key is present
+
Given an expression that specifies an element of a hash, returns true if the
specified element in the hash has ever been initialized, even if the
corresponding value is undefined.
=item exit
+=for Pod::Functions terminate this program
+
Evaluates EXPR and exits immediately with that value. Example:
$ans = <STDIN>;
defined C<END> routines first, but these C<END> routines may not
themselves abort the exit. Likewise any object destructors that need to
be called are called before the real exit. C<END> routines and destructors
-can change the exit status by modifying C<$?>. If this is a problem, you
+can change the exit status by modifying C<$?>. If this is a problem, you
can call C<POSIX:_exit($status)> to avoid END and destructor processing.
See L<perlmod> for details.
=item exp
+=for Pod::Functions raise I<e> to a power
+
Returns I<e> (the natural logarithm base) to the power of EXPR.
If EXPR is omitted, gives C<exp($_)>.
+=item fc EXPR
+X<fc> X<foldcase> X<casefold> X<fold-case> X<case-fold>
+
+=item fc
+
+=for Pod::Functions +fc return casefolded version of a string
+
+Returns the casefolded version of EXPR. This is the internal function
+implementing the C<\F> escape in double-quoted strings.
+
+Casefolding is the process of mapping strings to a form where case
+differences are erased; comparing two strings in their casefolded
+form is effectively a way of asking if two strings are equal,
+regardless of case.
+
+Roughly, if you ever found yourself writing this
+
+ lc($this) eq lc($that) # Wrong!
+ # or
+ uc($this) eq uc($that) # Also wrong!
+ # or
+ $this =~ /\Q$that/i # Right!
+
+Now you can write
+
+ fc($this) eq fc($that)
+
+And get the correct results.
+
+Perl only implements the full form of casefolding.
+For further information on casefolding, refer to
+the Unicode Standard, specifically sections 3.13 C<Default Case Operations>,
+4.2 C<Case-Normative>, and 5.18 C<Case Mappings>,
+available at L<http://www.unicode.org/versions/latest/>, as well as the
+Case Charts available at L<http://www.unicode.org/charts/case/>.
+
+If EXPR is omitted, uses C<$_>.
+
+This function behaves the same way under various pragma, such as in a locale,
+as L</lc> does.
+
+While the Unicode Standard defines two additional forms of casefolding,
+one for Turkic languages and one that never maps one character into multiple
+characters, these are not provided by the Perl core; However, the CPAN module
+C<Unicode::Casing> may be used to provide an implementation.
+
+This keyword is available only when the C<"fc"> feature is enabled,
+or when prefixed with C<CORE::>; See L<feature>. Alternately,
+include a C<use v5.16> or later to the current scope.
+
=item fcntl FILEHANDLE,FUNCTION,SCALAR
X<fcntl>
+=for Pod::Functions file control system call
+
Implements the fcntl(2) function. You'll probably have to say
use Fcntl;
=item __FILE__
X<__FILE__>
+=for Pod::Functions the name of the current source file
+
A special token that returns the name of the file in which it occurs.
=item fileno FILEHANDLE
X<fileno>
+=for Pod::Functions return file descriptor from filehandle
+
Returns the file descriptor for a filehandle, or undefined if the
filehandle is not open. If there is no real file descriptor at the OS
level, as can happen with filehandles connected to memory objects via
=item flock FILEHANDLE,OPERATION
X<flock> X<lock> X<locking>
+=for Pod::Functions lock an entire file with an advisory lock
+
Calls flock(2), or an emulation of it, on FILEHANDLE. Returns true
for success, false on failure. Produces a fatal error if used on a
machine that doesn't implement flock(2), fcntl(2) locking, or lockf(3).
=item fork
X<fork> X<child> X<parent>
+=for Pod::Functions create a new process just like this one
+
Does a fork(2) system call to create a new process running the
same program at the same point. It returns the child pid to the
parent process, C<0> to the child process, or C<undef> if the fork is
You should reopen those to F</dev/null> if it's any issue.
On some platforms such as Windows, where the fork() system call is not available,
-Perl can be built to emulate fork() in the Perl interpreter. The emulation is designed to,
-at the level of the Perl program, be as compatible as possible with the "Unix" fork().
+Perl can be built to emulate fork() in the Perl interpreter.
+The emulation is designed, at the level of the Perl program,
+to be as compatible as possible with the "Unix" fork().
However it has limitations that have to be considered in code intended to be portable.
See L<perlfork> for more details.
=item format
X<format>
+=for Pod::Functions declare a picture format with use by the write() function
+
Declare a picture format for use by the C<write> function. For
example:
=item formline PICTURE,LIST
X<formline>
+=for Pod::Functions internal function used for formats
+
This is an internal function used by C<format>s, though you may call it,
too. It formats (see L<perlform>) a list of values according to the
contents of PICTURE, placing the output into the format output
=item getc
+=for Pod::Functions get the next character from the filehandle
+
Returns the next character from the input file attached to FILEHANDLE,
or the undefined value at end of file or if there was an error (in
the latter case C<$!> is set). If FILEHANDLE is omitted, reads from
=item getlogin
X<getlogin> X<login>
+=for Pod::Functions return who logged in at this tty
+
This implements the C library function of the same name, which on most
systems returns the current login from F</etc/utmp>, if any. If it
returns the empty string, use C<getpwuid>.
=item getpeername SOCKET
X<getpeername> X<peer>
+=for Pod::Functions find the other end of a socket connection
+
Returns the packed sockaddr address of the other end of the SOCKET
connection.
=item getpgrp PID
X<getpgrp> X<group>
+=for Pod::Functions get process group
+
Returns the current process group for the specified PID. Use
a PID of C<0> to get the current process group for the
current process. Will raise an exception if used on a machine that
=item getppid
X<getppid> X<parent> X<pid>
+=for Pod::Functions get parent process ID
+
Returns the process id of the parent process.
-Note for Linux users: on Linux, the C functions C<getpid()> and
-C<getppid()> return different values from different threads. In order to
-be portable, this behavior is not reflected by the Perl-level function
-C<getppid()>, that returns a consistent value across threads. If you want
-to call the underlying C<getppid()>, you may use the CPAN module
-C<Linux::Pid>.
+Note for Linux users: Between v5.8.1 and v5.16.0 Perl would work
+around non-POSIX thread semantics the minority of Linux systems (and
+Debian GNU/kFreeBSD systems) that used LinuxThreads, this emulation
+has since been removed. See the documentation for L<$$|perlvar/$$> for
+details.
Portability issues: L<perlport/getppid>.
=item getpriority WHICH,WHO
X<getpriority> X<priority> X<nice>
+=for Pod::Functions get current nice value
+
Returns the current priority for a process, a process group, or a user.
(See L<getpriority(2)>.) Will raise a fatal exception if used on a
machine that doesn't implement getpriority(2).
X<setnetent> X<setprotoent> X<setservent> X<endpwent> X<endgrent> X<endhostent>
X<endnetent> X<endprotoent> X<endservent>
+=for Pod::Functions get passwd record given user login name
+
=item getgrnam NAME
+=for Pod::Functions get group record given group name
+
=item gethostbyname NAME
+=for Pod::Functions get host record given name
+
=item getnetbyname NAME
+=for Pod::Functions get networks record given name
+
=item getprotobyname NAME
+=for Pod::Functions get protocol record given name
+
=item getpwuid UID
+=for Pod::Functions get passwd record given user ID
+
=item getgrgid GID
+=for Pod::Functions get group record given group user ID
+
=item getservbyname NAME,PROTO
+=for Pod::Functions get services record given its name
+
=item gethostbyaddr ADDR,ADDRTYPE
+=for Pod::Functions get host record given its address
+
=item getnetbyaddr ADDR,ADDRTYPE
+=for Pod::Functions get network record given its address
+
=item getprotobynumber NUMBER
+=for Pod::Functions get protocol record numeric protocol
+
=item getservbyport PORT,PROTO
+=for Pod::Functions get services record given numeric port
+
=item getpwent
+=for Pod::Functions get next passwd record
+
=item getgrent
+=for Pod::Functions get next group record
+
=item gethostent
+=for Pod::Functions get next hosts record
+
=item getnetent
+=for Pod::Functions get next networks record
+
=item getprotoent
+=for Pod::Functions get next protocols record
+
=item getservent
+=for Pod::Functions get next services record
+
=item setpwent
+=for Pod::Functions prepare passwd file for use
+
=item setgrent
+=for Pod::Functions prepare group file for use
+
=item sethostent STAYOPEN
+=for Pod::Functions prepare hosts file for use
+
=item setnetent STAYOPEN
+=for Pod::Functions prepare networks file for use
+
=item setprotoent STAYOPEN
+=for Pod::Functions prepare protocols file for use
+
=item setservent STAYOPEN
+=for Pod::Functions prepare services file for use
+
=item endpwent
+=for Pod::Functions be done using passwd file
+
=item endgrent
+=for Pod::Functions be done using group file
+
=item endhostent
+=for Pod::Functions be done using hosts file
+
=item endnetent
+=for Pod::Functions be done using networks file
+
=item endprotoent
+=for Pod::Functions be done using protocols file
+
=item endservent
+=for Pod::Functions be done using services file
+
These routines are the same as their counterparts in the
system C library. In list context, the return values from the
various get routines are as follows:
=item getsockname SOCKET
X<getsockname>
+=for Pod::Functions retrieve the sockaddr for a given socket
+
Returns the packed sockaddr address of this end of the SOCKET connection,
in case you don't know the address because you have several different
IPs that the connection might have come in on.
=item getsockopt SOCKET,LEVEL,OPTNAME
X<getsockopt>
+=for Pod::Functions get socket options on a given socket
+
Queries the option named OPTNAME associated with SOCKET at a given LEVEL.
Options may exist at multiple protocol levels depending on the socket
type, but at least the uppermost socket level SOL_SOCKET (defined in the
-C<Socket> module) will exist. To query options at another level the
+C<Socket> module) will exist. To query options at another level the
protocol number of the appropriate protocol controlling the option
-should be supplied. For example, to indicate that an option is to be
+should be supplied. For example, to indicate that an option is to be
interpreted by the TCP protocol, LEVEL should be set to the protocol
number of TCP, which you can get using C<getprotobyname>.
The function returns a packed string representing the requested socket
option, or C<undef> on error, with the reason for the error placed in
-C<$!>. Just what is in the packed string depends on LEVEL and OPTNAME;
+C<$!>. Just what is in the packed string depends on LEVEL and OPTNAME;
consult getsockopt(2) for details. A common case is that the option is an
integer, in which case the result is a packed integer, which you can decode
using C<unpack> with the C<i> (or C<I>) format.
=item given BLOCK
-C<given> is analogous to the C<switch> keyword in other languages. C<given>
+=for Pod::Functions !RT #108848
+
+C<given> is analogous to the C<switch>
+keyword in other languages. C<given>
and C<when> are used in Perl to implement C<switch>/C<case> like statements.
Only available after Perl 5.10. For example:
}
}
-See L<perlsyn/"Switch statements"> for detailed information.
+See L<perlsyn/"Switch Statements"> for detailed information.
=item glob EXPR
X<glob> X<wildcard> X<filename, expansion> X<expand>
=item glob
+=for Pod::Functions expand filenames using wildcards
+
In list context, returns a (possibly empty) list of filename expansions on
-the value of EXPR such as the standard Unix shell F</bin/csh> would do. In
+the value of EXPR such as the standard Unix shell F</bin/csh> would do. In
scalar context, glob iterates through such filename expansions, returning
-undef when the list is exhausted. This is the internal function
-implementing the C<< <*.c> >> operator, but you can use it directly. If
+undef when the list is exhausted. This is the internal function
+implementing the C<< <*.c> >> operator, but you can use it directly. If
EXPR is omitted, C<$_> is used. The C<< <*.c> >> operator is discussed in
more detail in L<perlop/"I/O Operators">.
=item gmtime
+=for Pod::Functions convert UNIX time into record or string using Greenwich time
+
Works just like L</localtime> but the returned values are
localized for the standard Greenwich time zone.
=item goto &NAME
+=for Pod::Functions create spaghetti code
+
The C<goto-LABEL> form finds the statement labeled with LABEL and
-resumes execution there. It can't be used to get out of a block or
+resumes execution there. It can't be used to get out of a block or
subroutine given to C<sort>. It can be used to go almost anywhere
else within the dynamic scope, including out of subroutines, but it's
usually better to use some other construct such as C<last> or C<die>.
goto ("FOO", "BAR", "GLARCH")[$i];
As shown in this example, C<goto-EXPR> is exempt from the "looks like a
-function" rule. A pair of parentheses following it does not (necessarily)
-delimit its argument. C<goto("NE")."XT"> is equivalent to C<goto NEXT>.
+function" rule. A pair of parentheses following it does not (necessarily)
+delimit its argument. C<goto("NE")."XT"> is equivalent to C<goto NEXT>.
Use of C<goto-LABEL> or C<goto-EXPR> to jump into a construct is
deprecated and will issue a warning. Even then, it may not be used to
=item grep EXPR,LIST
+=for Pod::Functions locate elements in a list test true against a given criterion
+
This is similar in spirit to, but not the same as, grep(1) and its
relatives. In particular, it is not limited to using regular expressions.
=item hex
+=for Pod::Functions convert a string to a hexadecimal number
+
Interprets EXPR as a hex string and returns the corresponding value.
(To convert strings that might start with either C<0>, C<0x>, or C<0b>, see
L</oct>.) If EXPR is omitted, uses C<$_>.
Hex strings may only represent integers. Strings that would cause
integer overflow trigger a warning. Leading whitespace is not stripped,
-unlike oct(). To present something as hex, look into L</printf>,
+unlike oct(). To present something as hex, look into L</printf>,
L</sprintf>, and L</unpack>.
=item import LIST
X<import>
+=for Pod::Functions patch a module's namespace into your own
+
There is no builtin C<import> function. It is just an ordinary
method (subroutine) defined (or inherited) by modules that wish to export
names to another module. The C<use> function calls the C<import> method
=item index STR,SUBSTR
+=for Pod::Functions find a substring within a string
+
The index function searches for one string within another, but without
the wildcard-like behavior of a full regular-expression pattern match.
It returns the position of the first occurrence of SUBSTR in STR at
=item int
+=for Pod::Functions get the integer portion of a number
+
Returns the integer portion of EXPR. If EXPR is omitted, uses C<$_>.
You should not use this function for rounding: one because it truncates
towards C<0>, and two because machine representations of floating-point
=item ioctl FILEHANDLE,FUNCTION,SCALAR
X<ioctl>
+=for Pod::Functions system-dependent device control system call
+
Implements the ioctl(2) function. You'll probably first have to say
require "sys/ioctl.ph"; # probably in $Config{archlib}/sys/ioctl.ph
=item join EXPR,LIST
X<join>
+=for Pod::Functions join a list into a string using a separator
+
Joins the separate strings of LIST into a single string with fields
separated by the value of EXPR, and returns that new string. Example:
=item keys EXPR
-Returns a list consisting of all the keys of the named hash, or the indices
-of an array. (In scalar context, returns the number of keys or indices.)
+=for Pod::Functions retrieve list of indices from a hash
+
+Called in list context, returns a list consisting of all the keys of the
+named hash, or in Perl 5.12 or later only, the indices of an array. Perl
+releases prior to 5.12 will produce a syntax error if you try to use an
+array argument. In scalar context, returns the number of keys or indices.
The keys of a hash are returned in an apparently random order. The actual
random order is subject to change in future versions of Perl, but it
%hash> if you want to free the storage while C<%hash> is still in scope.
You can't shrink the number of buckets allocated for the hash using
C<keys> in this way (but you needn't worry about doing this by accident,
-as trying has no effect). C<keys @array> in an lvalue context is a syntax
+as trying has no effect). C<keys @array> in an lvalue context is a syntax
error.
Starting with Perl 5.14, C<keys> can take a scalar EXPR, which must contain
for (keys $hashref) { ... }
for (keys $obj->get_arrayref) { ... }
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious syntax errors, put this sort of thing at
+the top of your file to signal that your code will work I<only> on Perls of
+a recent vintage:
+
+ use 5.012; # so keys/values/each work on arrays
+ use 5.014; # so keys/values/each work on scalars (experimental)
+
See also C<each>, C<values>, and C<sort>.
=item kill SIGNAL, LIST
=item kill SIGNAL
X<kill> X<signal>
+=for Pod::Functions send a signal to a process or process group
+
Sends a signal to a list of processes. Returns the number of
processes successfully signaled (which is not necessarily the
same as the number actually killed).
L<perlport> for notes on the portability of this construct.
Unlike in the shell, if SIGNAL is negative, it kills process groups instead
-of processes. That means you usually want to use positive not negative signals.
+of processes. That means you usually
+want to use positive not negative signals.
You may also use a signal name in quotes.
The behavior of kill when a I<PROCESS> number is zero or negative depends on
=item last
+=for Pod::Functions exit a block prematurely
+
The C<last> command is like the C<break> statement in C (as used in
loops); it immediately exits the loop in question. If the LABEL is
omitted, the command refers to the innermost enclosing loop. The
=item lc
+=for Pod::Functions return lower-case version of a string
+
Returns a lowercased version of EXPR. This is the internal function
implementing the C<\L> escape in double-quoted strings.
=back
-=item Otherwise, if C<use locale> is in effect
+=item Otherwise, if C<use locale> (but not C<use locale ':not_characters'>) is in effect:
Respects current LC_CTYPE locale for code points < 256; and uses Unicode
semantics for the remaining code points (this last can only happen if
the input character unchanged, for all instances (and there aren't
many) where the 255/256 boundary would otherwise be crossed.
-=item Otherwise, If EXPR has the UTF8 flag set
+=item Otherwise, If EXPR has the UTF8 flag set:
Unicode semantics are used for the case change.
-=item Otherwise, if C<use feature 'unicode_strings'> is in effect:
+=item Otherwise, if C<use feature 'unicode_strings'> or C<use locale ':not_characters'>) is in effect:
Unicode semantics are used for the case change.
=item lcfirst
+=for Pod::Functions return a string with just the next letter in lower case
+
Returns the value of EXPR with the first character lowercased. This
is the internal function implementing the C<\l> escape in
double-quoted strings.
=item length
+=for Pod::Functions return the number of bytes in a string
+
Returns the length in I<characters> of the value of EXPR. If EXPR is
omitted, returns the length of C<$_>. If EXPR is undefined, returns
C<undef>.
=item __LINE__
X<__LINE__>
+=for Pod::Functions the current source line number
+
A special token that compiles to the current line number.
=item link OLDFILE,NEWFILE
X<link>
+=for Pod::Functions create a hard link in the filesystem
+
Creates a new filename linked to the old filename. Returns true for
success, false otherwise.
=item listen SOCKET,QUEUESIZE
X<listen>
+=for Pod::Functions register your socket as a server
+
Does the same thing that the listen(2) system call does. Returns true if
it succeeded, false otherwise. See the example in
L<perlipc/"Sockets: Client/Server Communication">.
=item local EXPR
X<local>
+=for Pod::Functions create a temporary value for a global variable (dynamic scoping)
+
You really probably want to be using C<my> instead, because C<local> isn't
what most people think of as "local". See
L<perlsub/"Private Variables via my()"> for details.
=item localtime
+=for Pod::Functions convert UNIX time into record or string using local time
+
Converts a time as returned by the time function to a 9-element list
with the time analyzed for the local time zone. Typically used as
follows:
print "$abbr[$mon] $mday";
# $mon=9, $mday=18 gives "Oct 18"
-C<$year> is the number of years since 1900, B<not> just the last two digits
-of the year. That is, C<$year> is C<123> in year 2023. The proper way
-to get a 4-digit year is simply:
+C<$year> contains the number of years since 1900. To get a 4-digit
+year write:
$year += 1900;
-Otherwise you create non-Y2K-compliant programs--and you wouldn't want
-to do that, would you?
-
To get the last two digits of the year (e.g., "01" in 2001) do:
$year = sprintf("%02d", $year % 100);
$now_string = localtime; # e.g., "Thu Oct 13 04:54:34 1994"
-This scalar value is B<not> locale-dependent but is a Perl builtin. For GMT
-instead of local time use the L</gmtime> builtin. See also the
+The format of this scalar value is B<not> locale-dependent
+but built into Perl. For GMT instead of local
+time use the L</gmtime> builtin. See also the
C<Time::Local> module (for converting seconds, minutes, hours, and such back to
the integer value returned by time()), and the L<POSIX> module's strftime(3)
and mktime(3) functions.
=item lock THING
X<lock>
+=for Pod::Functions +5.005 get a thread lock on a variable, subroutine, or method
+
This function places an advisory lock on a shared variable or referenced
object contained in I<THING> until the lock goes out of scope.
=item log
+=for Pod::Functions retrieve the natural logarithm for a number
+
Returns the natural logarithm (base I<e>) of EXPR. If EXPR is omitted,
returns the log of C<$_>. To get the
log of another base, use basic algebra:
=item lstat
+=for Pod::Functions stat a symbolic link
+
Does the same thing as the C<stat> function (including setting the
special C<_> filehandle) but stats a symbolic link instead of the file
the symbolic link points to. If symbolic links are unimplemented on
=item m//
+=for Pod::Functions match a string with a regular expression pattern
+
The match operator. See L<perlop/"Regexp Quote-Like Operators">.
=item map BLOCK LIST
=item map EXPR,LIST
+=for Pod::Functions apply a change to a list to get back a new list with the changes
+
Evaluates the BLOCK or EXPR for each element of LIST (locally setting
C<$_> to each element) and returns the list value composed of the
results of each such evaluation. In scalar context, returns the
my @squares = map { $_ > 5 ? ($_ * $_) : () } @numbers;
shows that number of returned elements can differ from the number of
-input elements. To omit an element, return an empty list ().
+input elements. To omit an element, return an empty list ().
This could also be achieved by writing
my @squares = map { $_ * $_ } grep { $_ > 5 } @numbers;
Map always returns a list, which can be
assigned to a hash such that the elements
-become key/value pairs. See L<perldata> for more details.
+become key/value pairs.
See L<perldata> for more details.
%hash = map { get_a_key_for($_) => $_ } @array;
can't be seen from the outside, avoiding any potential side-effects.
C<{> starts both hash references and blocks, so C<map { ...> could be either
-the start of map BLOCK LIST or map EXPR, LIST. Because Perl doesn't look
+the start of map BLOCK LIST or map EXPR, LIST. Because Perl doesn't look
ahead for the closing C<}> it has to take a guess at which it's dealing with
-based on what it finds just after the C<{>. Usually it gets it right, but if it
+based on what it finds just after the
+C<{>. Usually it gets it right, but if it
doesn't it won't realize something is wrong until it gets to the C<}> and
-encounters the missing (or unexpected) comma. The syntax error will be
+encounters the missing (or unexpected) comma. The syntax error will be
reported close to the C<}>, but you'll need to change something near the C<{>
such as using a unary C<+> to give Perl some help:
=item mkdir
+=for Pod::Functions create a directory
+
Creates the directory specified by FILENAME, with permissions
specified by MASK (as modified by C<umask>). If it succeeds it
returns true; otherwise it returns false and sets C<$!> (errno).
=item msgctl ID,CMD,ARG
X<msgctl>
+=for Pod::Functions SysV IPC message control operations
+
Calls the System V IPC function msgctl(2). You'll probably have to say
use IPC::SysV;
=item msgget KEY,FLAGS
X<msgget>
+=for Pod::Functions get SysV IPC message queue
+
Calls the System V IPC function msgget(2). Returns the message queue
id, or C<undef> on error. See also
L<perlipc/"SysV IPC"> and the documentation for C<IPC::SysV> and
=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
X<msgrcv>
+=for Pod::Functions receive a SysV IPC message from a message queue
+
Calls the System V IPC function msgrcv to receive a message from
message queue ID into variable VAR with a maximum message size of
SIZE. Note that when a message is received, the message type as a
=item msgsnd ID,MSG,FLAGS
X<msgsnd>
+=for Pod::Functions send a SysV IPC message to a message queue
+
Calls the System V IPC function msgsnd to send the message MSG to the
message queue ID. MSG must begin with the native long integer message
type, be followed by the length of the actual message, and then finally
=item my TYPE EXPR : ATTRS
+=for Pod::Functions declare and assign a local variable (lexical scoping)
+
A C<my> declares the listed variables to be local (lexically) to the
enclosing block, file, or C<eval>. If more than one value is listed,
the list must be placed in parentheses.
=item next
+=for Pod::Functions iterate a block prematurely
+
The C<next> command is like the C<continue> statement in C; it starts
the next iteration of the loop:
=item no VERSION
+=for Pod::Functions unimport some module symbols or semantics at compile time
+
See the C<use> function, of which C<no> is the opposite.
=item oct EXPR
=item oct
+=for Pod::Functions convert a string to an octal number
+
Interprets EXPR as an octal string and returns the corresponding
value. (If EXPR happens to start off with C<0x>, interprets it as a
hex string. If EXPR starts off with C<0b>, it is interpreted as a
=item open FILEHANDLE
+=for Pod::Functions open a file, pipe, or descriptor
+
Opens the file whose filename is given by EXPR, and associates it with
FILEHANDLE.
You can put a C<+> in front of the C<< > >> or C<< < >> to
indicate that you want both read and write access to the file; thus
C<< +< >> is almost always preferred for read/write updates--the
-C<< +> >> mode would clobber the file first. You cant usually use
+C<< +> >> mode would clobber the file first. You can't usually use
either read-write mode for updating textfiles, since they have
variable-length records. See the B<-i> switch in L<perlrun> for a
better approach. The file is created with permissions of C<0666>
You may (and usually should) use the three-argument form of open to specify
I/O layers (sometimes referred to as "disciplines") to apply to the handle
that affect how the input and output are processed (see L<open> and
-L<PerlIO> for more details). For example:
+L<PerlIO> for more details). For example:
open(my $fh, "<:encoding(UTF-8)", "filename")
|| die "can't open UTF-8 encoded filename: $!";
opens the UTF8-encoded file containing Unicode characters;
-see L<perluniintro>. Note that if layers are specified in the
+see L<perluniintro>. Note that if layers are specified in the
three-argument form, then default layers stored in ${^OPEN} (see L<perlvar>;
usually set by the B<open> pragma or the switch B<-CioD>) are ignored.
Those layers will also be ignored if you specifying a colon with no name
C<<< >> >>>, C<< < >>, C<< +> >>, C<<< +>> >>>, and C<< +< >>.
The mode you specify should match the mode of the original filehandle.
(Duping a filehandle does not take into account any existing contents
-of IO buffers.) If you use the three-argument form, then you can pass either a
+of IO buffers.) If you use the three-argument
+form, then you can pass either a
number, the name of a filehandle, or the normal "reference to a glob".
Here is a script that saves, redirects, and restores C<STDOUT> and
=item opendir DIRHANDLE,EXPR
X<opendir>
+=for Pod::Functions open a directory
+
Opens a directory named EXPR for processing by C<readdir>, C<telldir>,
C<seekdir>, C<rewinddir>, and C<closedir>. Returns true if successful.
DIRHANDLE may be an expression whose value can be used as an indirect
=item ord
+=for Pod::Functions find a character's numeric representation
+
Returns the numeric value of the first character of EXPR.
If EXPR is an empty string, returns 0. If EXPR is omitted, uses C<$_>.
(Note I<character>, not byte.)
=item our TYPE EXPR : ATTRS
+=for Pod::Functions +5.6.0 declare and assign a package variable (lexical scoping)
+
C<our> associates a simple name with a package variable in the current
package for use within the current scope. When C<use strict 'vars'> is in
effect, C<our> lets you use declared global variables without qualifying
with it.
The exact semantics and interface of TYPE and ATTRS are still
-evolving. TYPE is currently bound to the use of C<fields> pragma,
-and attributes are handled using the C<attributes> pragma, or starting
-from Perl 5.8.0 also via the C<Attribute::Handlers> module. See
+evolving. TYPE is currently bound to the use of the C<fields> pragma,
+and attributes are handled using the C<attributes> pragma, or, starting
+from Perl 5.8.0
, also via the C<Attribute::Handlers> module. See
L<perlsub/"Private Variables via my()"> for details, and L<fields>,
L<attributes>, and L<Attribute::Handlers>.
=item pack TEMPLATE,LIST
X<pack>
+=for Pod::Functions convert a list into a binary representation
+
Takes a LIST of values and converts it into a string using the rules
given by the TEMPLATE. The resulting string is the concatenation of
the converted values. Typically, each converted value looks
nNvV Treat integers as signed instead of unsigned.
@. Specify position as byte offset in the internal
- representation of the packed string. Efficient but
- dangerous.
+ representation of the packed string. Efficient
+ but dangerous.
> sSiIlLqQ Force big-endian byte-order on the type.
jJfFdDpP (The "big end" touches the construct.)
=back
The repeat count for C<u> is interpreted as the maximal number of bytes
-to encode per line of output, with 0, 1 and 2 replaced by 45. The repeat
+to encode per line of output, with 0, 1 and 2 replaced by 45. The repeat
count should not be more than 65.
=item *
within the structure itself as separate fields.
For C<pack>, you write I<length-item>C</>I<sequence-item>, and the
-I<length-item> describes how the length value is packed. Formats likely
+I<length-item> describes how the length value is packed. Formats likely
to be of most use are integer-packing ones like C<n> for Java strings,
C<w> for ASN.1 or SNMP, and C<N> for Sun XDR.
For C<pack>, I<sequence-item> may have a repeat count, in which case
the minimum of that and the number of available items is used as the argument
-for I<length-item>. If it has no repeat count or uses a '*', the number
+for I<length-item>. If it has no repeat count or uses a '*', the number
of available items is used.
For C<unpack>, an internal stack of integer arguments unpacked so far is
-used. You write C</>I<sequence-item> and the repeat count is obtained by
-popping off the last element from the stack. The I<sequence-item> must not
+used. You write C</>I<sequence-item> and the repeat count is obtained by
+popping off the last element from the stack. The I<sequence-item> must not
have a repeat count.
If I<sequence-item> refers to a string type (C<"A">, C<"a">, or C<"Z">),
Pack and unpack can operate in two modes: character mode (C<C0> mode) where
the packed string is processed per character, and UTF-8 mode (C<U0> mode)
where the packed string is processed in its UTF-8-encoded Unicode form on
-a byte-by-byte basis. Character mode is the default unless the format string
-starts with C<U>. You can always switch mode mid-format with an explicit
+a byte-by-byte basis. Character mode is the default
+unless the format string starts with C<U>. You
+can always switch mode mid-format with an explicit
C<C0> or C<U0> in the format. This mode remains in effect until the next
mode change, or until the end of the C<()> group it (directly) applies to.
A C<()> group is a sub-TEMPLATE enclosed in parentheses. A group may
take a repeat count either as postfix, or for unpack(), also via the C</>
template character. Within each repetition of a group, positioning with
-C<@> starts over at 0. Therefore, the result of
+C<@> starts over at 0. Therefore, the result of
pack("@1A((@2A)@3A)", qw[X Y Z])
C<x> and C<X> accept the C<!> modifier to act as alignment commands: they
jump forward or back to the closest position aligned at a multiple of C<count>
-characters. For example, to pack() or unpack() a C structure like
+characters. For example, to pack() or unpack() a C structure like
struct {
char c; /* one signed, 8-bit character */
$foo = pack("W4",0x24b6,0x24b7,0x24b8,0x24b9);
# same thing with Unicode circled letters.
$foo = pack("U4",0x24b6,0x24b7,0x24b8,0x24b9);
- # same thing with Unicode circled letters. You don't get the
+ # same thing with Unicode circled letters. You don't get the
# UTF-8 bytes because the U at the start of the format caused
# a switch to U0-mode, so the UTF-8 bytes get joined into
# characters
=item package NAMESPACE VERSION BLOCK
X<package> X<module> X<namespace> X<version>
+=for Pod::Functions declare a separate global namespace
+
Declares the BLOCK or the rest of the compilation unit as being in the
given namespace. The scope of the package declaration is either the
supplied code BLOCK or, in the absence of a BLOCK, from the declaration
See L<perlmod/"Packages"> for more information about packages, modules,
and classes. See L<perlsub> for other scoping issues.
+=item __PACKAGE__
+X<__PACKAGE__>
+
+=for Pod::Functions +5.004 the current package
+
+A special token that returns the name of the package in which it occurs.
+
=item pipe READHANDLE,WRITEHANDLE
X<pipe>
+=for Pod::Functions open a pair of connected filehandles
+
Opens a pair of connected pipes like the corresponding system call.
Note that if you set up a loop of piped processes, deadlock can occur
unless you are very careful. In addition, note that Perl's pipes use
on all newly opened file descriptors whose C<fileno>s are I<higher> than
the current value of $^F (by default 2 for C<STDERR>). See L<perlvar/$^F>.
-=item __PACKAGE__
-X<__PACKAGE__>
-
-A special token that returns the name of the package in which it occurs.
-
=item pop ARRAY
X<pop> X<stack>
=item pop
+=for Pod::Functions remove the last element from an array and return it
+
Pops and returns the last value of the array, shortening the array by
one element.
automatically. This aspect of C<pop> is considered highly experimental.
The exact behaviour may change in a future version of Perl.
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious syntax errors, put this sort of thing at
+the top of your file to signal that your code will work I<only> on Perls of
+a recent vintage:
+
+ use 5.014; # so push/pop/etc work on scalars (experimental)
+
=item pos SCALAR
X<pos> X<match, position>
=item pos
+=for Pod::Functions find or set the offset for the last/next m//g search
+
Returns the offset of where the last C<m//g> search left off for the
variable in question (C<$_> is used when the variable is not
-specified). Note that 0 is a valid match offset. C<undef> indicates
+specified). Note that 0 is a valid match offset. C<undef> indicates
that the search position is reset (usually due to match failure, but
can also be because no match has yet been run on the scalar).
C<pos> directly accesses the location used by the regexp engine to
store the offset, so assigning to C<pos> will change that offset, and
so will also influence the C<\G> zero-width assertion in regular
-expressions. Both of these effects take place for the next match, so
+expressions. Both of these effects take place for the next match, so
you can't affect the position with C<pos> during the current match,
such as in C<(?{pos() = 5})> or C<s//pos() = 5/e>.
=item print
+=for Pod::Functions output a list to a filehandle
+
Prints a string or a list of strings. Returns true if successful.
FILEHANDLE may be a scalar variable containing the name of or a reference
to the filehandle, thus introducing one level of indirection. (NOTE: If
FILEHANDLE is a variable and the next token is a term, it may be
misinterpreted as an operator unless you interpose a C<+> or put
-parentheses around the arguments.) If FILEHANDLE is omitted, prints to the
+parentheses around the arguments.) If FILEHANDLE is omitted, prints to the
last selected (see L</select>) output handle. If LIST is omitted, prints
C<$_> to the currently selected output handle. To use FILEHANDLE alone to
print the content of C<$_> to it, you must use a real filehandle like
=item printf
+=for Pod::Functions output a formatted list to a filehandle
+
Equivalent to C<print FILEHANDLE sprintf(FORMAT, LIST)>, except that C<$\>
(the output record separator) is not appended. The first argument of the
-list will be interpreted as the C<printf> format. See
+list will be interpreted as the C<printf> format. See
L<sprintf|/sprintf FORMAT, LIST> for an
-explanation of the format argument. If you omit the LIST, C<$_> is used;
+explanation of the format argument. If you omit the LIST, C<$_> is used;
to use FILEHANDLE without a LIST, you must use a real filehandle like
-C<FH>, not an indirect one like C<$fh>. If C<use locale> is in effect and
+C<FH>, not an indirect one like C<$fh>. If C<use locale> (including
+C<use locale ':not_characters'>) is in effect and
POSIX::setlocale() has been called, the character used for the decimal
separator in formatted floating-point numbers is affected by the LC_NUMERIC
locale setting. See L<perllocale> and L<POSIX>.
=item prototype FUNCTION
X<prototype>
+=for Pod::Functions +5.002 get the prototype (if any) of a subroutine
+
Returns the prototype of a function as a string (or C<undef> if the
function has no prototype). FUNCTION is a reference to, or the name of,
the function whose prototype you want to retrieve.
=item push EXPR,LIST
+=for Pod::Functions append one or more elements to an array
+
Treats ARRAY as a stack by appending the values of LIST to the end of
ARRAY. The length of ARRAY increases by the length of LIST. Has the same
effect as
automatically. This aspect of C<push> is considered highly experimental.
The exact behaviour may change in a future version of Perl.
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious syntax errors, put this sort of thing at
+the top of your file to signal that your code will work I<only> on Perls of
+a recent vintage:
+
+ use 5.014; # so push/pop/etc work on scalars (experimental)
+
=item q/STRING/
+=for Pod::Functions singly quote a string
+
=item qq/STRING/
-=item qx/STRING/
+=for Pod::Functions doubly quote a string
=item qw/STRING/
+=for Pod::Functions quote a list of words
+
+=item qx/STRING/
+
+=for Pod::Functions backquote quote a string
+
Generalized quotes. See L<perlop/"Quote-Like Operators">.
=item qr/STRING/
+=for Pod::Functions +5.005 compile pattern
+
Regexp-like quote. See L<perlop/"Regexp Quote-Like Operators">.
=item quotemeta EXPR
=item quotemeta
-Returns the value of EXPR with all non-"word"
-characters backslashed. (That is, all characters not matching
+=for Pod::Functions quote regular expression magic characters
+
+Returns the value of EXPR with all the ASCII non-"word"
+characters backslashed. (That is, all ASCII characters not matching
C</[A-Za-z_0-9]/> will be preceded by a backslash in the
returned string, regardless of any locale settings.)
This is the internal function implementing
the C<\Q> escape in double-quoted strings.
+(See below for the behavior on non-ASCII code points.)
If EXPR is omitted, uses C<$_>.
quotemeta (and C<\Q> ... C<\E>) are useful when interpolating strings into
regular expressions, because by default an interpolated variable will be
-considered a mini-regular expression. For example:
+considered a mini-regular expression. For example:
my $sentence = 'The quick brown fox jumped over the lazy dog';
my $substring = 'quick.*?fox';
my $quoted_substring = quotemeta($substring);
$sentence =~ s{$quoted_substring}{big bad wolf};
-Will both leave the sentence as is. Normally, when accepting literal string
+Will both leave the sentence as is.
+Normally, when accepting literal string
input from the user, quotemeta() or C<\Q> must be used.
-In Perl 5.14, all characters whose code points are above 127 are not
-quoted in UTF8-encoded strings, but all are quoted in UTF-8 strings.
-It is planned to change this behavior in 5.16, but the exact rules
-haven't been determined yet.
+In Perl v5.14, all non-ASCII characters are quoted in non-UTF-8-encoded
+strings, but not quoted in UTF-8 strings.
+
+Starting in Perl v5.16, Perl adopted a Unicode-defined strategy for
+quoting non-ASCII characters; the quoting of ASCII characters is
+unchanged.
+
+Also unchanged is the quoting of non-UTF-8 strings when outside the
+scope of a C<use feature 'unicode_strings'>, which is to quote all
+characters in the upper Latin1 range. This provides complete backwards
+compatibility for old programs which do not use Unicode. (Note that
+C<unicode_strings> is automatically enabled within the scope of a
+S<C<use v5.12>> or greater.)
+
+Within the scope of C<use locale>, all non-ASCII Latin1 code points
+are quoted whether the string is encoded as UTF-8 or not. As mentioned
+above, locale does not affect the quoting of ASCII-range characters.
+This protects against those locales where characters such as C<"|"> are
+considered to be word characters.
+
+Otherwise, Perl quotes non-ASCII characters using an adaptation from
+Unicode (see L<http://www.unicode.org/reports/tr31/>.)
+The only code points that are quoted are those that have any of the
+Unicode properties: Pattern_Syntax, Pattern_White_Space, White_Space,
+Default_Ignorable_Code_Point, or General_Category=Control.
+
+Of these properties, the two important ones are Pattern_Syntax and
+Pattern_White_Space. They have been set up by Unicode for exactly this
+purpose of deciding which characters in a regular expression pattern
+should be quoted. No character that can be in an identifier has these
+properties.
+
+Perl promises, that if we ever add regular expression pattern
+metacharacters to the dozen already defined
+(C<\ E<verbar> ( ) [ { ^ $ * + ? .>), that we will only use ones that have the
+Pattern_Syntax property. Perl also promises, that if we ever add
+characters that are considered to be white space in regular expressions
+(currently mostly affected by C</x>), they will all have the
+Pattern_White_Space property.
+
+Unicode promises that the set of code points that have these two
+properties will never change, so something that is not quoted in v5.16
+will never need to be quoted in any future Perl release. (Not all the
+code points that match Pattern_Syntax have actually had characters
+assigned to them; so there is room to grow, but they are quoted
+whether assigned or not. Perl, of course, would never use an
+unassigned code point as an actual metacharacter.)
+
+Quoting characters that have the other 3 properties is done to enhance
+the readability of the regular expression and not because they actually
+need to be quoted for regular expression purposes (characters with the
+White_Space property are likely to be indistinguishable on the page or
+screen from those with the Pattern_White_Space property; and the other
+two properties contain non-printing characters).
=item rand EXPR
X<rand> X<random>
=item rand
+=for Pod::Functions retrieve the next pseudorandom number
+
Returns a random fractional number greater than or equal to C<0> and less
than the value of EXPR. (EXPR should be positive.) If EXPR is
omitted, the value C<1> is used. Currently EXPR with the value C<0> is
=item read FILEHANDLE,SCALAR,LENGTH
+=for Pod::Functions fixed-length buffered input from a filehandle
+
Attempts to read LENGTH I<characters> of data into variable SCALAR
from the specified FILEHANDLE. Returns the number of characters
actually read, C<0> at end of file, or undef if there was an error (in
=item readdir DIRHANDLE
X<readdir>
+=for Pod::Functions get a directory from a directory handle
+
Returns the next directory entry for a directory opened by C<opendir>.
If used in list context, returns all the rest of the entries in the
directory. If there are no more entries, returns the undefined value in
}
closedir $dh;
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious failures, put this sort of thing at the
+top of your file to signal that your code will work I<only> on Perls of a
+recent vintage:
+
+ use 5.012; # so readdir assigns to $_ in a lone while test
+
=item readline EXPR
=item readline
X<readline> X<gets> X<fgets>
+=for Pod::Functions fetch a record from a file
+
Reads from the filehandle whose typeglob is contained in EXPR (or from
C<*ARGV> if EXPR is not provided). In scalar context, each call reads and
returns the next line until end-of-file is reached, whereupon the
}
Note that you have can't handle C<readline> errors that way with the
-C<ARGV> filehandle. In that case, you have to open each element of
+C<ARGV> filehandle. In that case, you have to open each element of
C<@ARGV> yourself since C<eof> handles C<ARGV> differently.
foreach my $arg (@ARGV) {
=item readlink
+=for Pod::Functions determine where a symbolic link is pointing
+
Returns the value of a symbolic link, if symbolic links are
implemented. If not, raises an exception. If there is a system
error, returns the undefined value and sets C<$!> (errno). If EXPR is
=item readpipe
X<readpipe>
+=for Pod::Functions execute a system command and collect standard output
+
EXPR is executed as a system command.
The collected standard output of the command is returned.
In scalar context, it comes back as a single (potentially
=item recv SOCKET,SCALAR,LENGTH,FLAGS
X<recv>
+=for Pod::Functions receive a message over a Socket
+
Receives a message on a socket. Attempts to receive LENGTH characters
of data into variable SCALAR from the specified SOCKET filehandle.
SCALAR will be grown or shrunk to the length actually read. Takes the
=item redo
+=for Pod::Functions start this loop iteration over again
+
The C<redo> command restarts the loop block without evaluating the
conditional again. The C<continue> block, if any, is not executed. If
the LABEL is omitted, the command refers to the innermost enclosing
=item ref
+=for Pod::Functions find out the type of thing being referenced
+
Returns a non-empty string if EXPR is a reference, the empty
-string otherwise. If EXPR
+string otherwise. If EXPR
is not specified, C<$_> will be used. The value returned depends on the
type of thing the reference is a reference to.
Builtin types include:
}
The return value C<LVALUE> indicates a reference to an lvalue that is not
-a variable. You get this from taking the reference of function calls like
-C<pos()> or C<substr()>. C<VSTRING> is returned if the reference points
+a variable. You get this from taking the reference of function calls like
+C<pos()> or C<substr()>. C<VSTRING> is returned if the reference points
to a L<version string|perldata/"Version Strings">.
The result C<Regexp> indicates that the argument is a regular expression
=item rename OLDNAME,NEWNAME
X<rename> X<move> X<mv> X<ren>
+=for Pod::Functions change a filename
+
Changes the name of a file; an existing file NEWNAME will be
clobbered. Returns true for success, false otherwise.
=item require
+=for Pod::Functions load in external functions from a library at runtime
+
Demands a version of Perl specified by VERSION, or demands some semantics
specified by EXPR or by C<$_> if EXPR is not supplied.
Now that you understand how C<require> looks for files with a
bareword argument, there is a little extra functionality going on behind
the scenes. Before C<require> looks for a "F<.pm>" extension, it will
-first look for a similar filename with a "F<.pmc>" extension. If this file
+first look for a similar filename with a "F<.pmc>" extension. If this file
is found, it will be loaded in place of any file ending in a "F<.pm>"
extension.
=item 2
-A reference to a subroutine. If there is no filehandle (previous item),
+A reference to a subroutine. If there is no filehandle (previous item),
then this subroutine is expected to generate one line of source code per
call, writing the line into C<$_> and returning 1, then finally at end of
file returning 0. If there is a filehandle, then the subroutine will be
=item 3
-Optional state for the subroutine. The state is passed in as C<$_[1]>. A
+Optional state for the subroutine. The state is passed in as C<$_[1]>. A
reference to the subroutine itself is passed in as C<$_[0]>.
=back
push @INC, Foo->new(...);
These hooks are also permitted to set the %INC entry
-corresponding to the files they have loaded. See L<perlvar/%INC>.
+corresponding to the files they have loaded.
See L<perlvar/%INC>.
For a yet-more-powerful import facility, see L</use> and L<perlmod>.
=item reset
+=for Pod::Functions clear all variables of a given name
+
Generally used in a C<continue> block at the end of a loop to clear
variables and reset C<??> searches so that they work again. The
expression is interpreted as a list of single characters (hyphens
=item return
+=for Pod::Functions get out of a function early
+
Returns from a subroutine, C<eval>, or C<do FILE> with the value
given in EXPR. Evaluation of EXPR may be in list, scalar, or void
context, depending on how the return value will be used, and the context
=item reverse LIST
X<reverse> X<rev> X<invert>
+=for Pod::Functions flip a string or a list
+
In list context, returns a list value consisting of the elements
of LIST in the opposite order. In scalar context, concatenates the
elements of LIST and returns a string value with all characters
=item rewinddir DIRHANDLE
X<rewinddir>
+=for Pod::Functions reset directory handle
+
Sets the current position to the beginning of the directory for the
C<readdir> routine on DIRHANDLE.
=item rindex STR,SUBSTR
+=for Pod::Functions right-to-left substring search
+
Works just like index() except that it returns the position of the I<last>
occurrence of SUBSTR in STR. If POSITION is specified, returns the
last occurrence beginning at or before that position.
=item rmdir
+=for Pod::Functions remove a directory
+
Deletes the directory specified by FILENAME if that directory is
empty. If it succeeds it returns true; otherwise it returns false and
sets C<$!> (errno). If FILENAME is omitted, uses C<$_>.
=item s///
+=for Pod::Functions replace a pattern with a string
+
The substitution operator. See L<perlop/"Regexp Quote-Like Operators">.
=item say FILEHANDLE LIST
=item say
+=for Pod::Functions +say output a list to a filehandle, appending a newline
+
Just like C<print>, but implicitly appends a newline. C<say LIST> is
simply an abbreviation for C<{ local $\ = "\n"; print LIST }>. To use
FILEHANDLE without a LIST to print the contents of C<$_> to it, you must
=item scalar EXPR
X<scalar> X<context>
+=for Pod::Functions force a scalar context
+
Forces EXPR to be interpreted in scalar context and returns the value
of EXPR.
=item seek FILEHANDLE,POSITION,WHENCE
X<seek> X<fseek> X<filehandle, position>
+=for Pod::Functions reposition file pointer for random-access I/O
+
Sets FILEHANDLE's position, just like the C<fseek> call of C<stdio>.
FILEHANDLE may be an expression whose value gives the name of the
filehandle. The values for WHENCE are C<0> to set the new position
=item seekdir DIRHANDLE,POS
X<seekdir>
+=for Pod::Functions reposition directory pointer
+
Sets the current position for the C<readdir> routine on DIRHANDLE. POS
must be a value returned by C<telldir>. C<seekdir> also has the same caveats
about possible directory compaction as the corresponding system library
=item select
+=for Pod::Functions reset default output or do I/O multiplexing
+
Returns the currently selected filehandle. If FILEHANDLE is supplied,
sets the new current default filehandle for output. This has two
effects: first, a C<write> or a C<print> without a filehandle
On some Unixes, select(2) may report a socket file descriptor as "ready for
reading" even when no data is available, and thus any subsequent C<read>
-would block. This can be avoided if you always use O_NONBLOCK on the
-socket. See select(2) and fcntl(2) for further details.
+would block. This can be avoided if you always use O_NONBLOCK on the
+socket. See select(2) and fcntl(2) for further details.
The standard C<IO::Select> module provides a user-friendlier interface
to C<select>, mostly because it does all the bit-mask work for you.
=item semctl ID,SEMNUM,CMD,ARG
X<semctl>
+=for Pod::Functions SysV semaphore control operations
+
Calls the System V IPC function semctl(2). You'll probably have to say
use IPC::SysV;
=item semget KEY,NSEMS,FLAGS
X<semget>
+=for Pod::Functions get set of SysV semaphores
+
Calls the System V IPC function semget(2). Returns the semaphore id, or
the undefined value on error. See also
L<perlipc/"SysV IPC">, C<IPC::SysV>, C<IPC::SysV::Semaphore>
=item semop KEY,OPSTRING
X<semop>
+=for Pod::Functions SysV semaphore operations
+
Calls the System V IPC function semop(2) for semaphore operations
such as signalling and waiting. OPSTRING must be a packed array of
semop structures. Each semop structure can be generated with
=item send SOCKET,MSG,FLAGS
+=for Pod::Functions send a message over a socket
+
Sends a message on a socket. Attempts to send the scalar MSG to the SOCKET
filehandle. Takes the same flags as the system call of the same name. On
unconnected sockets, you must specify a destination to I<send to>, in which
=item setpgrp PID,PGRP
X<setpgrp> X<group>
+=for Pod::Functions set the process group of a process
+
Sets the current process group for the specified PID, C<0> for the current
process. Raises an exception when used on a machine that doesn't
implement POSIX setpgid(2) or BSD setpgrp(2). If the arguments are omitted,
=item setpriority WHICH,WHO,PRIORITY
X<setpriority> X<priority> X<nice> X<renice>
+=for Pod::Functions set a process's nice value
+
Sets the current priority for a process, a process group, or a user.
(See setpriority(2).) Raises an exception when used on a machine
that doesn't implement setpriority(2).
=item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
X<setsockopt>
+=for Pod::Functions set some socket options
+
Sets the socket option requested. Returns C<undef> on error.
Use integer constants provided by the C<Socket> module for
LEVEL and OPNAME. Values for LEVEL can also be obtained from
=item shift
+=for Pod::Functions remove the first element of an array, and return it
+
Shifts the first value of the array off and returns it, shortening the
array by 1 and moving everything down. If there are no elements in the
array, returns the undefined value. If ARRAY is omitted, shifts the
automatically. This aspect of C<shift> is considered highly experimental.
The exact behaviour may change in a future version of Perl.
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious syntax errors, put this sort of thing at
+the top of your file to signal that your code will work I<only> on Perls of
+a recent vintage:
+
+ use 5.014; # so push/pop/etc work on scalars (experimental)
+
See also C<unshift>, C<push>, and C<pop>. C<shift> and C<unshift> do the
same thing to the left end of an array that C<pop> and C<push> do to the
right end.
=item shmctl ID,CMD,ARG
X<shmctl>
+=for Pod::Functions SysV shared memory operations
+
Calls the System V IPC function shmctl. You'll probably have to say
use IPC::SysV;
=item shmget KEY,SIZE,FLAGS
X<shmget>
+=for Pod::Functions get SysV shared memory segment identifier
+
Calls the System V IPC function shmget. Returns the shared memory
segment id, or C<undef> on error.
See also L<perlipc/"SysV IPC"> and C<IPC::SysV> documentation.
X<shmread>
X<shmwrite>
+=for Pod::Functions read SysV shared memory
+
=item shmwrite ID,STRING,POS,SIZE
+=for Pod::Functions write SysV shared memory
+
Reads or writes the System V shared memory segment ID starting at
position POS for size SIZE by attaching to it, copying in/out, and
detaching from it. When reading, VAR must be a variable that will
hold the data read. When writing, if STRING is too long, only SIZE
bytes are used; if STRING is too short, nulls are written to fill out
SIZE bytes. Return true if successful, false on error.
-shmread() taints the variable. See also L<perlipc/"SysV IPC">,
+shmread() taints the variable.
See also L<perlipc/"SysV IPC">,
C<IPC::SysV>, and the C<IPC::Shareable> module from CPAN.
Portability issues: L<perlport/shmread> and L<perlport/shmwrite>.
=item shutdown SOCKET,HOW
X<shutdown>
+=for Pod::Functions close down just half of a socket connection
+
Shuts down a socket connection in the manner indicated by HOW, which
has the same interpretation as in the syscall of the same name.
=item sin
+=for Pod::Functions return the sine of a number
+
Returns the sine of EXPR (expressed in radians). If EXPR is omitted,
returns sine of C<$_>.
=item sleep
+=for Pod::Functions block for some number of seconds
+
Causes the script to sleep for (integer) EXPR seconds, or forever if no
argument is given. Returns the integer number of seconds actually slept.
distribution) provides usleep(). You may also use Perl's four-argument
version of select() leaving the first three arguments undefined, or you
might be able to use the C<syscall> interface to access setitimer(2) if
-your system supports it. See L<perlfaq8> for details.
+your system supports it.
See L<perlfaq8> for details.
See also the POSIX module's C<pause> function.
=item socket SOCKET,DOMAIN,TYPE,PROTOCOL
X<socket>
+=for Pod::Functions create a socket
+
Opens a socket of the specified kind and attaches it to filehandle
SOCKET. DOMAIN, TYPE, and PROTOCOL are specified the same as for
the syscall of the same name. You should C<use Socket> first
=item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
X<socketpair>
+=for Pod::Functions create a pair of sockets
+
Creates an unnamed pair of sockets in the specified domain, of the
specified type. DOMAIN, TYPE, and PROTOCOL are specified the same as
for the syscall of the same name. If unimplemented, raises an exception.
=item sort LIST
+=for Pod::Functions sort a list of values
+
In list context, this sorts the LIST and returns the sorted list value.
In scalar context, the behaviour of C<sort()> is undefined.
You also cannot exit out of the sort block or subroutine using any of the
loop control operators described in L<perlsyn> or with C<goto>.
-When C<use locale> is in effect, C<sort LIST> sorts LIST according to the
+When C<use locale> (but not C<use locale 'not_characters'>) is in
+effect, C<sort LIST> sorts LIST according to the
current collation locale. See L<perllocale>.
sort() returns aliases into the original list, much as a for loop's index
@articles = sort {$a cmp $b} @files;
# now case-insensitively
- @articles = sort {uc($a) cmp uc($b)} @files;
+ @articles = sort {fc($a) cmp fc($b)} @files;
# same thing in reversed order
@articles = sort {$b cmp $a} @files;
my @new = sort {
($b =~ /=(\d+)/)[0] <=> ($a =~ /=(\d+)/)[0]
||
- uc($a) cmp uc($b)
+ fc($a) cmp fc($b)
} @old;
# same thing, but much more efficiently;
my @nums = @caps = ();
for (@old) {
push @nums, ( /=(\d+)/ ? $1 : undef );
- push @caps, uc($_);
+ push @caps, fc($_);
}
my @new = @old[ sort {
sort { $b->[1] <=> $a->[1]
||
$a->[2] cmp $b->[2]
- } map { [$_, /=(\d+)/, uc($_)] } @old;
+ } map { [$_, /=(\d+)/, fc($_)] } @old;
# using a prototype allows you to use any comparison subroutine
# as a sort subroutine (including other package's subroutines)
@new = sort { substr($a, 3, 5) cmp substr($b, 3, 5) } @old;
Warning: syntactical care is required when sorting the list returned from
-a function. If you want to sort the list returned by the function call
+a function. If you want to sort the list returned by the function call
C<find_records(@key)>, you can use:
@contact = sort { $a cmp $b } find_records @key;
=item splice ARRAY or EXPR
+=for Pod::Functions add or remove elements anywhere in an array
+
Removes the elements designated by OFFSET and LENGTH from an array, and
replaces them with the elements of LIST, if any. In list context,
returns the elements removed from the array. In scalar context,
If LENGTH is omitted, removes everything from OFFSET onward.
If LENGTH is negative, removes the elements from OFFSET onward
except for -LENGTH elements at the end of the array.
-If both OFFSET and LENGTH are omitted, removes everything. If OFFSET is
+If both OFFSET and LENGTH are omitted, removes everything. If OFFSET is
past the end of the array, Perl issues a warning, and splices at the
end of the array.
automatically. This aspect of C<splice> is considered highly experimental.
The exact behaviour may change in a future version of Perl.
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious syntax errors, put this sort of thing at
+the top of your file to signal that your code will work I<only> on Perls of
+a recent vintage:
+
+ use 5.014; # so push/pop/etc work on scalars (experimental)
+
=item split /PATTERN/,EXPR,LIMIT
X<split>
=item split
-Splits the string EXPR into a list of strings and returns that list. By
-default, empty leading fields are preserved, and empty trailing ones are
-deleted. (If all fields are empty, they are considered to be trailing.)
+=for Pod::Functions split up a string using a regexp delimiter
+
+Splits the string EXPR into a list of strings and returns the
+list in list context, or the size of the list in scalar context.
+
+If only PATTERN is given, EXPR defaults to C<$_>.
+
+Anything in EXPR that matches PATTERN is taken to be a separator
+that separates the EXPR into substrings (called "I<fields>") that
+do B<not> include the separator. Note that a separator may be
+longer than one character or even have no characters at all (the
+empty string, which is a zero-width match).
+
+The PATTERN need not be constant; an expression may be used
+to specify a pattern that varies at runtime.
+
+If PATTERN matches the empty string, the EXPR is split at the match
+position (between characters). As an example, the following:
+
+ print join(':', split('b', 'abc')), "\n";
+
+uses the 'b' in 'abc' as a separator to produce the output 'a:c'.
+However, this:
-In scalar context, returns the number of fields found.
+ print join(':', split('', 'abc')), "\n";
-If EXPR is omitted, splits the C<$_> string. If PATTERN is also omitted,
-splits on whitespace (after skipping any leading whitespace). Anything
-matching PATTERN is taken to be a delimiter separating the fields. (Note
-that the delimiter may be longer than one character.)
+uses empty string matches as separators to produce the output
+'a:b:c'; thus, the empty string may be used to split EXPR into a
+list of its component characters.
+
+As a special case for C<split>, the empty pattern given in
+L<match operator|perlop/"m/PATTERN/msixpodualgc"> syntax (C<//>) specifically matches the empty string, which is contrary to its usual
+interpretation as the last successful match.
+
+If PATTERN is C</^/>, then it is treated as if it used the
+L<multiline modifier|perlreref/OPERATORS> (C</^/m>), since it
+isn't much use otherwise.
+
+As another special case, C<split> emulates the default behavior of the
+command line tool B<awk> when the PATTERN is either omitted or a I<literal
+string> composed of a single space character (such as S<C<' '>> or
+S<C<"\x20">>, but not e.g. S<C</ />>). In this case, any leading
+whitespace in EXPR is removed before splitting occurs, and the PATTERN is
+instead treated as if it were C</\s+/>; in particular, this means that
+I<any> contiguous whitespace (not just a single space character) is used as
+a separator. However, this special treatment can be avoided by specifying
+the pattern S<C</ />> instead of the string S<C<" ">>, thereby allowing
+only a single space character to be a separator.
+
+If omitted, PATTERN defaults to a single space, S<C<" ">>, triggering
+the previously described I<awk> emulation.
If LIMIT is specified and positive, it represents the maximum number
-of fields the EXPR will be split into, though the actual number of
-fields returned depends on the number of times PATTERN matches within
-EXPR. If LIMIT is unspecified or zero, trailing null fields are
-stripped (which potential users of C<pop> would do well to remember).
-If LIMIT is negative, it is treated as if an arbitrarily large LIMIT
-had been specified. Note that splitting an EXPR that evaluates to the
-empty string always returns the empty list, regardless of the LIMIT
-specified.
+of fields into which the EXPR may be split; in other words, LIMIT is
+one greater than the maximum number of times EXPR may be split. Thus,
+the LIMIT value C<1> means that EXPR may be split a maximum of zero
+times, producing a maximum of one field (namely, the entire value of
+EXPR). For instance:
-A pattern matching the empty string (not to be confused with
-an empty pattern C<//>, which is just one member of the set of patterns
-matching the empty string), splits EXPR into individual
-characters. For example:
+ print join(':', split(//, 'abc', 1)), "\n";
- print join(':', split(/ */, 'hi there')), "\n";
+produces the output 'abc', and this:
-produces the output 'h:i:t:h:e:r:e'.
+ print join(':', split(//, 'abc', 2)), "\n";
-As a special case for C<split>, the empty pattern C<//> specifically
-matches the empty string; this is not be confused with the normal use
-of an empty pattern to mean the last successful match. So to split
-a string into individual characters, the following:
+produces the output 'a:bc', and each of these:
- print join(':', split(//, 'hi there')), "\n";
+ print join(':', split(//, 'abc', 3)), "\n";
+ print join(':', split(//, 'abc', 4)), "\n";
-produces the output 'h:i: :t:h:e:r:e'.
+produces the output 'a:b:c'.
-Empty leading fields are produced when there are positive-width matches at
-the beginning of the string; a zero-width match at the beginning of
-the string does not produce an empty field. For example:
+If LIMIT is negative, it is treated as if it were instead arbitrarily
+large; as many fields as possible are produced.
- print join(':', split(/(?=\w)/, 'hi there!'));
+If LIMIT is omitted (or, equivalently, zero), then it is usually
+treated as if it were instead negative but with the exception that
+trailing empty fields are stripped (empty leading fields are always
+preserved); if all fields are empty, then all fields are considered to
+be trailing (and are thus stripped in this case). Thus, the following:
-produces the output 'h:i :t:h:e:r:e!'. Empty trailing fields, on the other
-hand, are produced when there is a match at the end of the string (and
-when LIMIT is given and is not 0), regardless of the length of the match.
-For example:
+ print join(':', split(',', 'a,b,c,,,')), "\n";
- print join(':', split(//, 'hi there!', -1)), "\n";
- print join(':', split(/\W/, 'hi there!', -1)), "\n";
+produces the output 'a:b:c', but the following:
-produce the output 'h:i: :t:h:e:r:e:!:' and 'hi:there:', respectively,
-both with an empty trailing field.
+ print join(':', split(',', 'a,b,c,,,', -1)), "\n";
-The LIMIT parameter can be used to split a line partially
+produces the output 'a:b:c:::'.
- ($login, $passwd, $remainder) = split(/:/, $_, 3);
+In time-critical applications, it is worthwhile to avoid splitting
+into more fields than necessary. Thus, when assigning to a list,
+if LIMIT is omitted (or zero), then LIMIT is treated as though it
+were one larger than the number of variables in the list; for the
+following, LIMIT is implicitly 4:
-When assigning to a list, if LIMIT is omitted, or zero, Perl supplies
-a LIMIT one larger than the number of variables in the list, to avoid
-unnecessary work. For the list above LIMIT would have been 4 by
-default. In time critical applications it behooves you not to split
-into more fields than you really need.
+ ($login, $passwd, $remainder) = split(/:/);
-If the PATTERN contains parentheses, additional list elements are
-created from each matching substring in the delimiter.
+Note that splitting an EXPR that evaluates to the empty string always
+produces zero fields, regardless of the LIMIT specified.
- split(/([,-])/, "1-10,20", 3);
+An empty leading field is produced when there is a positive-width
+match at the beginning of EXPR. For instance:
-produces the list value
+ print join(':', split(/ /, ' abc')), "\n";
- (1, '-', 10, ',', 20)
+produces the output ':abc'. However, a zero-width match at the
+beginning of EXPR never produces an empty field, so that:
-If you had the entire header of a normal Unix email message in $header,
-you could split it up into fields and their values this way:
+ print join(':', split(//, ' abc'));
- $header =~ s/\n(?=\s)//g; # fix continuation lines
- %hdrs = (UNIX_FROM => split /^(\S*?):\s*/m, $header);
+produces the output S<' :a:b:c'> (rather than S<': :a:b:c'>).
-The pattern C</PATTERN/> may be replaced with an expression to specify
-patterns that vary at runtime. (To do runtime compilation only once,
-use C</$variable/o>.)
+An empty trailing field, on the other hand, is produced when there is a
+match at the end of EXPR, regardless of the length of the match
+(of course, unless a non-zero LIMIT is given explicitly, such fields are
+removed, as in the last example). Thus:
-As a special case, specifying a PATTERN of space (S<C<' '>>) will split on
-white space just as C<split> with no arguments does. Thus, S<C<split(' ')>> can
-be used to emulate B<awk>'s default behavior, whereas S<C<split(/ /)>>
-will give you as many initial null fields (empty string) as there are leading spaces.
-A C<split> on C</\s+/> is like a S<C<split(' ')>> except that any leading
-whitespace produces a null first field. A C<split> with no arguments
-really does a S<C<split(' ', $_)>> internally.
+ print join(':', split(//, ' abc', -1)), "\n";
-A PATTERN of C</^/> is treated as if it were C</^/m>, since it isn't
-much use otherwise.
+produces the output S<' :a:b:c:'>.
-Example:
+If the PATTERN contains
+L<capturing groups|perlretut/Grouping things and hierarchical matching>,
+then for each separator, an additional field is produced for each substring
+captured by a group (in the order in which the groups are specified,
+as per L<backreferences|perlretut/Backreferences>); if any group does not
+match, then it captures the C<undef> value instead of a substring. Also,
+note that any such additional field is produced whenever there is a
+separator (that is, whenever a split occurs), and such an additional field
+does B<not> count towards the LIMIT. Consider the following expressions
+evaluated in list context (each returned list is provided in the associated
+comment):
- open(PASSWD, '/etc/passwd');
- while (<PASSWD>) {
- chomp;
- ($login, $passwd, $uid, $gid,
- $gcos, $home, $shell) = split(/:/);
- #...
- }
+ split(/-|,/, "1-10,20", 3)
+ # ('1', '10', '20')
-As with regular pattern matching, any capturing parentheses that are not
-matched in a C<split()> will be set to C<undef> when returned:
+ split(/(-|,)/, "1-10,20", 3)
+ # ('1', '-', '10', ',', '20')
- @fields = split /(A)|B/, "1A2B3";
- # @fields is (1, 'A', 2, undef, 3)
+ split(/-|(,)/, "1-10,20", 3)
+ # ('1', undef, '10', ',', '20')
+
+ split(/(-)|,/, "1-10,20", 3)
+ # ('1', '-', '10', undef, '20')
+
+ split(/(-)|(,)/, "1-10,20", 3)
+ # ('1', '-', undef, '10', undef, ',', '20')
=item sprintf FORMAT, LIST
X<sprintf>
+=for Pod::Functions formatted print into a string
+
Returns a string formatted by the usual C<printf> conventions of the C
library function C<sprintf>. See below for more details
and see L<sprintf(3)> or L<printf(3)> on your system for an explanation of
therefore unavailable from Perl.
Unlike C<printf>, C<sprintf> does not do what you probably mean when you
-pass it an array as your first argument. The array is given scalar context,
+pass it an array as your first argument.
+The array is given scalar context,
and instead of using the 0th element of the array as the format, Perl will
use the count of elements in the array as the format, which is almost never
useful.
=item format parameter index
-An explicit format parameter index, such as C<2$>. By default sprintf
+An explicit format parameter index, such as C<2$>. By default sprintf
will format the next unused argument in the list, but this allows you
to take the arguments out of order:
=item vector flag
This flag tells Perl to interpret the supplied string as a vector of
-integers, one for each character in the string. Perl applies the format to
+integers, one for each character in the string. Perl applies the format to
each integer in turn, then joins the resulting strings with a separator (a
-dot C<.> by default). This can be useful for displaying ordinal values of
+dot C<.> by default). This can be useful for displaying ordinal values of
characters in arbitrary strings:
printf "%vd", "AB\x{100}"; # prints "65.66.256"
=item (minimum) width
Arguments are usually formatted to be only as wide as required to
-display the given value. You can override the width by putting
+display the given value. You can override the width by putting
a number here, or get the width from the next argument (with C<*>)
or from a specified argument (e.g., with C<*2$>):
=item size
For numeric conversions, you can specify the size to interpret the
-number as using C<l>, C<h>, C<V>, C<q>, C<L>, or C<ll>. For integer
+number as using C<l>, C<h>, C<V>, C<q>, C<L>, or C<ll>. For integer
conversions (C<d u o x X b i D U O>), numbers are usually assumed to be
whatever the default integer size is on your platform (usually 32 or 64
bits), but you can override this to use instead one of the standard C types,
For floating-point conversions (C<e f g E F G>), numbers are usually assumed
to be the default floating-point size on your platform (double or long double),
but you can force "long double" with C<q>, C<L>, or C<ll> if your
-platform supports them. You can find out whether your Perl supports long
+platform supports them. You can find out whether your Perl supports long
doubles via L<Config>:
use Config;
=item order of arguments
Normally, sprintf() takes the next unused argument as the value to
-format for each format specification. If the format specification
+format for each format specification. If the format specification
uses C<*> to require additional arguments, these are consumed from
the argument list in the order they appear in the format
specification I<before> the value to format. Where an argument is
=back
-If C<use locale> is in effect and POSIX::setlocale() has been called,
+If C<use locale> (including C<use locale 'not_characters'>) is in effect
+and POSIX::setlocale() has been called,
the character used for the decimal separator in formatted floating-point
numbers is affected by the LC_NUMERIC locale. See L<perllocale>
and L<POSIX>.
=item sqrt
+=for Pod::Functions square root function
+
Return the positive square root of EXPR. If EXPR is omitted, uses
C<$_>. Works only for non-negative operands unless you've
loaded the C<Math::Complex> module.
=item srand
+=for Pod::Functions seed the random number generator
+
Sets and returns the random number seed for the C<rand> operator.
-The point of the function is to "seed" the C<rand> function so that
-C<rand> can produce a different sequence each time you run your
-program. When called with a parameter, C<srand> uses that for the seed;
-otherwise it (semi-)randomly chooses a seed. In either case, starting with
-Perl 5.14, it returns the seed.
+The point of the function is to "seed" the C<rand> function so that C<rand>
+can produce a different sequence each time you run your program. When
+called with a parameter, C<srand> uses that for the seed; otherwise it
+(semi-)randomly chooses a seed. In either case, starting with Perl 5.14,
+it returns the seed. To signal that your code will work I<only> on Perls
+of a recent vintage:
+
+ use 5.014; # so srand returns the seed
If C<srand()> is not called explicitly, it is called implicitly without a
parameter at the first use of the C<rand> operator. However, this was not true
=item stat
+=for Pod::Functions get a file's status information
+
Returns a 13-element list giving the status info for a file, either
the file opened via FILEHANDLE or DIRHANDLE, or named by EXPR. If EXPR is
omitted, it stats C<$_> (not C<_>!). Returns the empty list if C<stat> fails. Typically
(The epoch was at 00:00 January 1, 1970 GMT.)
-(*) Not all fields are supported on all filesystem types. Notably, the
+(*) Not all fields are supported on all filesystem types. Notably, the
ctime field is non-portable. In particular, you cannot expect it to be a
"creation time"; see L<perlport/"Files and Filesystems"> for details.
=item state TYPE EXPR : ATTRS
+=for Pod::Functions +state declare and assign a persistent lexical variable
+
C<state> declares a lexically scoped variable, just like C<my>.
However, those variables will never be reinitialized, contrary to
lexical variables that are reinitialized each time their enclosing block
=item study
+=for Pod::Functions optimize input data for repeated searches
+
Takes extra time to study SCALAR (C<$_> if unspecified) in anticipation of
doing many pattern matches on the string before it is next modified.
This may or may not save time, depending on the nature and number of
=item sub NAME (PROTO) : ATTRS BLOCK
+=for Pod::Functions declare a subroutine, possibly anonymously
+
This is subroutine definition, not a real function I<per se>. Without a
BLOCK it's just a forward declaration. Without a NAME, it's an anonymous
function declaration, so does return a value: the CODE ref of the closure
=item __SUB__
X<__SUB__>
+=for Pod::Functions +current_sub the current subroutine, or C<undef> if not in a subroutine
+
A special token that returns the a reference to the current subroutine, or
C<undef> outside of a subroutine.
=item substr EXPR,OFFSET
+=for Pod::Functions get or alter a portion of a string
+
Extracts a substring out of EXPR and returns it. First character is at
offset zero. If OFFSET is negative, starts
that far back from the end of the string. If LENGTH is omitted, returns
=item symlink OLDFILE,NEWFILE
X<symlink> X<link> X<symbolic link> X<link, symbolic>
+=for Pod::Functions create a symbolic link to a file
+
Creates a new filename symbolically linked to the old filename.
Returns C<1> for success, C<0> otherwise. On systems that don't support
symbolic links, raises an exception. To check for that,
=item syscall NUMBER, LIST
X<syscall> X<system call>
+=for Pod::Functions execute an arbitrary system call
+
Calls the system call specified as the first element of the list,
passing the remaining elements as arguments to the system call. If
unimplemented, raises an exception. The arguments are interpreted
=item sysopen FILEHANDLE,FILENAME,MODE,PERMS
+=for Pod::Functions +5.002 open a file, pipe, or descriptor
+
Opens the file whose filename is given by FILENAME, and associates it with
FILEHANDLE. If FILEHANDLE is an expression, its value is used as the real
-filehandle wanted; an undefined scalar will be suitably autovivified. This
+filehandle wanted; an undefined scalar will be suitably autovivified. This
function calls the underlying operating system's I<open>(2) function with the
parameters FILENAME, MODE, and PERMS.
Note that C<sysopen> depends on the fdopen() C library function.
On many Unix systems, fdopen() is known to fail when file descriptors
-exceed a certain value, typically 255. If you need more file
+exceed a certain value, typically 255. If you need more file
descriptors than that, consider rebuilding Perl to use the C<sfio>
library, or perhaps using the POSIX::open() function.
=item sysread FILEHANDLE,SCALAR,LENGTH
+=for Pod::Functions fixed-length unbuffered input from a filehandle
+
Attempts to read LENGTH bytes of data into variable SCALAR from the
specified FILEHANDLE, using the read(2). It bypasses
buffered IO, so mixing this with other kinds of reads, C<print>,
=item sysseek FILEHANDLE,POSITION,WHENCE
X<sysseek> X<lseek>
+=for Pod::Functions +5.004 position I/O pointer on handle used with sysread and syswrite
+
Sets FILEHANDLE's system position in bytes using lseek(2). FILEHANDLE may
be an expression whose value gives the name of the filehandle. The values
for WHENCE are C<0> to set the new position to POSITION; C<1> to set the it
=item system PROGRAM LIST
+=for Pod::Functions run a separate program
+
Does exactly the same thing as C<exec LIST>, except that a fork is
done first and the parent process waits for the child process to
exit. Note that argument processing varies depending on the
The return value is the exit status of the program as returned by the
C<wait> call. To get the actual exit value, shift right by eight (see
-below). See also L</exec>. This is I<not> what you want to use to capture
+below). See also L</exec>. This is I<not> what you want to use to capture
the output from a command; for that you should use merely backticks or
C<qx//>, as described in L<perlop/"`STRING`">. Return value of -1
indicates a failure to start the program or an error of the wait(2) system
See L<perlop/"`STRING`"> and L</exec> for details.
Since C<system> does a C<fork> and C<wait> it may affect a C<SIGCHLD>
-handler. See L<perlipc> for details.
+handler.
See L<perlipc> for details.
Portability issues: L<perlport/system>.
=item syswrite FILEHANDLE,SCALAR
+=for Pod::Functions fixed-length unbuffered output to a filehandle
+
Attempts to write LENGTH bytes of data from variable SCALAR to the
specified FILEHANDLE, using write(2). If LENGTH is
not specified, writes whole SCALAR. It bypasses buffered IO, so
=item tell
+=for Pod::Functions get current seekpointer on a filehandle
+
Returns the current position I<in bytes> for FILEHANDLE, or -1 on
error. FILEHANDLE may be an expression whose value gives the name of
the actual filehandle. If FILEHANDLE is omitted, assumes the file
=item telldir DIRHANDLE
X<telldir>
+=for Pod::Functions get current seekpointer on a directory handle
+
Returns the current position of the C<readdir> routines on DIRHANDLE.
Value may be given to C<seekdir> to access a particular location in a
directory. C<telldir> has the same caveats about possible directory
=item tie VARIABLE,CLASSNAME,LIST
X<tie>
+=for Pod::Functions +5.002 bind a variable to an object class
+
This function binds a variable to a package class that will provide the
implementation for the variable. VARIABLE is the name of the variable
to be enchanted. CLASSNAME is the name of a class implementing objects
=item tied VARIABLE
X<tied>
+=for Pod::Functions get a reference to the object underlying a tied variable
+
Returns a reference to the object underlying VARIABLE (the same value
that was originally returned by the C<tie> call that bound the variable
to a package.) Returns the undefined value if VARIABLE isn't tied to a
=item time
X<time> X<epoch>
+=for Pod::Functions return number of seconds since 1970
+
Returns the number of non-leap seconds since whatever time the system
considers to be the epoch, suitable for feeding to C<gmtime> and
-C<localtime>. On most systems the epoch is 00:00:00 UTC, January 1, 1970;
+C<localtime>. On most systems the epoch is 00:00:00 UTC, January 1, 1970;
a prominent exception being Mac OS Classic which uses 00:00:00, January 1,
1904 in the current local time zone for its epoch.
=item times
X<times>
+=for Pod::Functions return elapsed time for self and child processes
+
Returns a four-element list giving the user and system times in
seconds for this process and any exited children of this process.
=item tr///
+=for Pod::Functions transliterate a string
+
The transliteration operator. Same as C<y///>. See
L<perlop/"Quote and Quote-like Operators">.
=item truncate EXPR,LENGTH
+=for Pod::Functions shorten a file
+
Truncates the file opened on FILEHANDLE, or named by EXPR, to the
specified length. Raises an exception if truncate isn't implemented
on your system. Returns true if successful, C<undef> on error.
=item uc
+=for Pod::Functions return upper-case version of a string
+
Returns an uppercased version of EXPR. This is the internal function
implementing the C<\U> escape in double-quoted strings.
It does not attempt to do titlecase mapping on initial letters. See
=item ucfirst
+=for Pod::Functions return a string with just the next letter in upper case
+
Returns the value of EXPR with the first character in uppercase
(titlecase in Unicode). This is the internal function implementing
the C<\u> escape in double-quoted strings.
=item umask
+=for Pod::Functions set file creation mode mask
+
Sets the umask for the process to EXPR and returns the previous value.
If EXPR is omitted, merely returns the current umask.
=item undef
+=for Pod::Functions remove a variable or function definition
+
Undefines the value of EXPR, which must be an lvalue. Use only on a
scalar value, an array (using C<@>), a hash (using C<%>), a subroutine
(using C<&>), or a typeglob (using C<*>). Saying C<undef $hash{$key}>
=item unlink
-Deletes a list of files. On success, it returns the number of files
-it successfully deleted. On failure, it returns false and sets C<$!>
+=for Pod::Functions remove one link to a file
+
+Deletes a list of files. On success, it returns the number of files
+it successfully deleted. On failure, it returns false and sets C<$!>
(errno):
my $unlinked = unlink 'a', 'b', 'c';
}
Note: C<unlink> will not attempt to delete directories unless you are
-superuser and the B<-U> flag is supplied to Perl. Even if these
+superuser and the B<-U> flag is supplied to Perl. Even if these
conditions are met, be warned that unlinking a directory can inflict
damage on your filesystem. Finally, using C<unlink> on directories is
not supported on many operating systems. Use C<rmdir> instead.
=item unpack TEMPLATE
+=for Pod::Functions convert binary structure into normal perl variables
+
C<unpack> does the reverse of C<pack>: it takes a string
and expands it out into a list of values.
(In scalar context, it returns merely the first value produced.)
See L</pack> for more examples and notes.
-=item untie VARIABLE
-X<untie>
-
-Breaks the binding between a variable and a package.
-(See L<tie|/tie VARIABLE,CLASSNAME,LIST>.)
-Has no effect if the variable is not tied.
-
=item unshift ARRAY,LIST
X<unshift>
=item unshift EXPR,LIST
+=for Pod::Functions prepend more elements to the beginning of a list
+
Does the opposite of a C<shift>. Or the opposite of a C<push>,
depending on how you look at it. Prepends list to the front of the
array and returns the new number of elements in the array.
automatically. This aspect of C<unshift> is considered highly
experimental. The exact behaviour may change in a future version of Perl.
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious syntax errors, put this sort of thing at
+the top of your file to signal that your code will work I<only> on Perls of
+a recent vintage:
+
+ use 5.014; # so push/pop/etc work on scalars (experimental)
+
+=item untie VARIABLE
+X<untie>
+
+=for Pod::Functions break a tie binding to a variable
+
+Breaks the binding between a variable and a package.
+(See L<tie|/tie VARIABLE,CLASSNAME,LIST>.)
+Has no effect if the variable is not tied.
+
=item use Module VERSION LIST
X<use> X<module> X<import>
=item use VERSION
+=for Pod::Functions load in a module at compile time and import its namespace
+
Imports some semantics into the current package from the named module,
generally by aliasing certain subroutine or variable names into your
package. It is exactly equivalent to
C<use VERSION> also enables all features available in the requested
version as defined by the C<feature> pragma, disabling any features
-not in the current version's feature bundle. See L<feature>.
+not in the requested version's feature bundle. See L<feature>.
Similarly, if the specified Perl version is greater than or equal to
5.11.0, strictures are enabled lexically as
with C<use strict>. Any explicit use of
=item utime LIST
X<utime>
+=for Pod::Functions set a file's last access and modify times
+
Changes the access and modification times on each file of a list of
files. The first two elements of the list must be the NUMERIC access
and modification times, in that order. Returns the number of files
Since Perl 5.7.2, if the first two elements of the list are C<undef>,
the utime(2) syscall from your C library is called with a null second
-argument. On most systems, this will set the file's access and
+argument. On most systems, this will set the file's access and
modification times to the current time (i.e., equivalent to the example
above) and will work even on files you don't own provided you have write
permission:
=item values EXPR
-Returns a list consisting of all the values of the named hash, or the values
-of an array. (In scalar context, returns the number of values.)
+=for Pod::Functions return a list of the values in a hash
-The values are returned in an apparently random order. The actual
-random order is subject to change in future versions of Perl, but it
-is guaranteed to be the same order as either the C<keys> or C<each>
-function would produce on the same (unmodified) hash. Since Perl
-5.8.1 the ordering is different even between different runs of Perl
-for security reasons (see L<perlsec/"Algorithmic Complexity Attacks">).
+In list context, returns a list consisting of all the values of the named
+hash. In Perl 5.12 or later only, will also return a list of the values of
+an array; prior to that release, attempting to use an array argument will
+produce a syntax error. In scalar context, returns the number of values.
+
+When called on a hash, the values are returned in an apparently random
+order. The actual random order is subject to change in future versions of
+Perl, but it is guaranteed to be the same order as either the C<keys> or
+C<each> function would produce on the same (unmodified) hash. Since Perl
+5.8.1 the ordering is different even between different runs of Perl for
+security reasons (see L<perlsec/"Algorithmic Complexity Attacks">).
As a side effect, calling values() resets the HASH or ARRAY's internal
-iterator;
-see L</each>. (In particular, calling values() in void context resets
-the iterator with no other overhead. Apart from resetting the iterator,
-C<values @array> in list context is the same as plain C<@array>.
-We recommend that you use void context C<keys @array> for this, but reasoned
-that it taking C<values @array> out would require more documentation than
-leaving it in.)
+iterator, see L</each>. (In particular, calling values() in void context
+resets the iterator with no other overhead. Apart from resetting the
+iterator, C<values @array> in list context is the same as plain C<@array>.
+(We recommend that you use void context C<keys @array> for this, but
+reasoned that taking C<values @array> out would require more
+documentation than leaving it in.)
Note that the values are not copied, which means modifying them will
modify the contents of the hash:
for (values $hashref) { ... }
for (values $obj->get_arrayref) { ... }
+To avoid confusing would-be users of your code who are running earlier
+versions of Perl with mysterious syntax errors, put this sort of thing at
+the top of your file to signal that your code will work I<only> on Perls of
+a recent vintage:
+
+ use 5.012; # so keys/values/each work on arrays
+ use 5.014; # so keys/values/each work on scalars (experimental)
+
See also C<keys>, C<each>, and C<sort>.
=item vec EXPR,OFFSET,BITS
X<vec> X<bit> X<bit vector>
+=for Pod::Functions test or set particular bits in a string
+
Treats the string in EXPR as a bit vector made up of elements of
width BITS and returns the value of the element specified by OFFSET
as an unsigned integer. BITS therefore specifies the number of bits
=item wait
X<wait>
+=for Pod::Functions wait for any child process to die
+
Behaves like wait(2) on your system: it waits for a child
process to terminate and returns the pid of the deceased process, or
C<-1> if there are no child processes. The status is returned in C<$?>
being automatically reaped, as described in L<perlipc>.
If you use wait in your handler for $SIG{CHLD} it may accidentally for the
-child created by qx() or system(). See L<perlipc> for details.
+child created by qx() or system().
See L<perlipc> for details.
Portability issues: L<perlport/wait>.
=item waitpid PID,FLAGS
X<waitpid>
+=for Pod::Functions wait for a particular child process to die
+
Waits for a particular child process to terminate and returns the pid of
the deceased process, or C<-1> if there is no such child process. On some
systems, a value of 0 indicates that there are processes still running.
=item wantarray
X<wantarray> X<context>
+=for Pod::Functions get void vs scalar vs list context of current subroutine call
+
Returns true if the context of the currently executing subroutine or
C<eval> is looking for a list value. Returns false if the context is
looking for a scalar. Returns the undefined value if the context is
=item warn LIST
X<warn> X<warning> X<STDERR>
+=for Pod::Functions print debugging info
+
Prints the value of LIST to STDERR. If the last element of LIST does
not end in a newline, it appends the same file/line number text as C<die>
does.
=item when BLOCK
-C<when> is analogous to the C<case> keyword in other languages. Used with a
+=for Pod::Functions !RT #108848
+
+C<when> is analogous to the C<case>
+keyword in other languages. Used with a
C<foreach> loop or the experimental C<given> block, C<when> can be used in
Perl to implement C<switch>/C<case> like statements. Available as a
statement after Perl 5.10 and as a statement modifier after 5.14.
}
}
-See L<perlsyn/"Switch statements"> for detailed information.
+See L<perlsyn/"Switch Statements"> for detailed information.
=item write FILEHANDLE
X<write>
=item write
+=for Pod::Functions print a picture record
+
Writes a formatted record (possibly multi-line) to the specified FILEHANDLE,
using the format associated with that file. By default the format for
a file is the one having the same name as the filehandle, but the
room on the current page for the formatted record, the page is advanced by
writing a form feed, a special top-of-page format is used to format the new
page header before the record is written. By default, the top-of-page
-format is the name of the filehandle with "_TOP" appended. This would be a
+format is the name of the filehandle with "_TOP" appended. This would be a
problem with autovivified filehandles, but it may be dynamically set to the
format of your choice by assigning the name to the C<$^> variable while
that filehandle is selected. The number of lines remaining on the current
=item y///
+=for Pod::Functions transliterate a string
+
The transliteration operator. Same as C<tr///>. See
L<perlop/"Quote and Quote-like Operators">.
=back
+=head2 Non-function Keywords by Cross-reference
+
+=head3 perldata
+
+=over
+
+=item __DATA__
+
+=item __END__
+
+These keywords are documented in L<perldata>.
+
+=back
+
+=head3 perlmod
+
+=over
+
+=item BEGIN
+
+=item CHECK
+
+=item DESTROY
+
+=item END
+
+=item INIT
+
+=item UNITCHECK
+
+These keywords are documented in L<perlmod>.
+
+=back
+
+=head3 perlop
+
+=over
+
+=item and
+
+=item cmp
+
+=item eq
+
+=item ge
+
+=item gt
+
+=item if
+
+=item le
+
+=item lt
+
+=item ne
+
+=item not
+
+=item or
+
+=item x
+
+=item xor
+
+These operators are documented in L<perlop>.
+
+=back
+
+=head3 perlsub
+
+=over
+
+=item AUTOLOAD
+
+These are documented in L<perlsub>.
+
+=back
+
+=head3 perlsyn
+
+=over
+
+=item else
+
+=item elseif
+
+=item elsif
+
+=item for
+
+=item foreach
+
+=item unless
+
+=item until
+
+=item while
+
+These flow-control keywords are documented in L<perlsyn>.
+
+=back
+
=cut
https://perl5.git.perl.org / perl5.git / blobdiff