argument is omitted, tests C<$_>, except for C<-t>, which tests STDIN.
Unless otherwise documented, it returns C<1> for true and C<''> for false, or
the undefined value if the file doesn't exist. Despite the funny
-names, precedence is the same as any other named unary operator, and
-the argument may be parenthesized like any other unary operator. The
+names, precedence is the same as any other named unary operator. The
operator may be any of:
-r File is readable by effective uid/gid.
of this version of Perl therefore refers to "layers" rather than to
"disciplines". Now back to the regularly scheduled documentation...>
-To mark FILEHANDLE as UTF-8, use C<:utf8>.
+To mark FILEHANDLE as UTF-8, use C<:utf8> or C<:encoding(utf8)>.
+C<:utf8> just marks the data as UTF-8 without further checking,
+while C<:encoding(utf8)> checks the data for actually being valid
+UTF-8. More details can be found in L<PerlIO::encoding>.
In general, binmode() should be called after open() but before any I/O
is done on the filehandle. Calling binmode() will normally flush any
If you chomp a list, each element is chomped, and the total number of
characters removed is returned.
-If the C<encoding> pragma is in scope then the lengths returned are
-calculated from the length of C<$/> in Unicode characters, which is not
-always the same as the length of C<$/> in the native encoding.
-
Note that parentheses are necessary when you're chomping anything
that is not a simple variable. This is because C<chomp $cwd = `pwd`;>
is interpreted as C<(chomp $cwd) = `pwd`;>, rather than as
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. Note that characters from 128
-to 255 (inclusive) are by default not encoded in UTF-8 Unicode for
-backward compatibility reasons (but see L<encoding>).
+chr(0x263a) is a Unicode smiley face.
Negative values give the Unicode replacement character (chr(0xfffd)),
except under the L<bytes> pragma, where low eight bits of the value
For the reverse, use L</ord>.
-Note that under the C<bytes> pragma the NUMBER is masked to
-the low eight bits.
+Note that characters from 128 to 255 (inclusive) are by default
+internally not encoded as UTF-8 for backward compatibility reasons.
-See L<perlunicode> and L<encoding> for more about Unicode.
+See L<perlunicode> for more about Unicode.
=item chroot FILENAME
X<chroot> X<root>
be open any more when the program is reincarnated, with possible
resulting confusion on the part of Perl.
-This function is now largely obsolete, partly because it's very
-hard to convert a core file into an executable, and because the
-real compiler backends for generating portable bytecode and compilable
-C code have superseded it. That's why you should now invoke it as
-C<CORE::dump()>, if you don't want to be warned against a possible
+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
+it as C<CORE::dump()>, if you don't want to be warned against a possible
typo.
-If you're looking to use L<dump> to speed up your program, consider
-generating bytecode or native C code as described in L<perlcc>. If
-you're just trying to accelerate a CGI script, consider using the
-C<mod_perl> extension to B<Apache>, or the CPAN module, CGI::Fast.
-You might also consider autoloading or selfloading, which at least
-make your program I<appear> to run faster.
-
=item each HASH
X<each> X<hash, iterator>
Note the I<characters>: if the EXPR is in Unicode, you will get the
number of characters, not the number of bytes. To get the length
-in bytes, use C<do { use bytes; length(EXPR) }>, see L<bytes>.
+of the internal string in bytes, use C<bytes::length(EXPR)>, see
+L<bytes>. Note that the internal encoding is variable, and the number
+of bytes usually meaningless. To get the number of bytes that the
+string would have when encoded as UTF-8, use
+C<length(Encoding::encode_utf8(EXPR))>.
=item link OLDFILE,NEWFILE
X<link>
=item no Module
+=item no VERSION
+
See the C<use> function, of which C<no> is the opposite.
=item oct EXPR
that affect how the input and output are processed (see L<open> and
L<PerlIO> for more details). For example
- open(FH, "<:utf8", "file")
+ open(FH, "<:encoding(UTF-8)", "file")
will open the UTF-8 encoded file containing Unicode characters,
see L<perluniintro>. Note that if layers are specified in the
uses C<$_>.
For the reverse, see L</chr>.
-See L<perlunicode> and L<encoding> for more about Unicode.
+See L<perlunicode> for more about Unicode.
=item our EXPR
X<our> X<global>
H A hex string (high nybble first).
c A signed char (8-bit) value.
- C An unsigned C char (octet) even under Unicode. Should normally not
- be used. See U and W instead.
+ C An unsigned char (octet) value.
W An unsigned char value (can be greater than 255).
s A signed short (16-bit) value.
P A pointer to a structure (fixed-length string).
u A uuencoded string.
- U A Unicode character number. Encodes to UTF-8 internally
- (or UTF-EBCDIC in EBCDIC platforms).
+ U A Unicode character number. Encodes to a character in character mode
+ and UTF-8 (or UTF-EBCDIC in EBCDIC platforms) in byte mode.
w A BER compressed integer (not an ASN.1 BER, see perlpacktut for
details). Its bytes represent an unsigned integer in base 128,
closedir DIR;
=item readline EXPR
+
+=item readline
X<readline> X<gets> X<fgets>
-Reads from the filehandle whose typeglob is contained in EXPR. In scalar
-context, each call reads and returns the next line, until end-of-file is
-reached, whereupon the subsequent call returns undef. In list context,
-reads until end-of-file is reached and returns a list of lines. Note that
-the notion of "line" used here is however you may have defined it
-with C<$/> or C<$INPUT_RECORD_SEPARATOR>). See L<perlvar/"$/">.
+Reads from the filehandle whose typeglob is contained in EXPR (or from
+*ARGV if EXPR is not provided). In scalar context, each call reads and
+returns the next line, until end-of-file is reached, whereupon the
+subsequent call returns undef. In list context, reads until end-of-file
+is reached and returns a list of lines. Note that the notion of "line"
+used here is however you may have defined it with C<$/> or
+C<$INPUT_RECORD_SEPARATOR>). See L<perlvar/"$/">.
When C<$/> is set to C<undef>, when readline() is in scalar
context (i.e. file slurp mode), and when an empty file is read, it
omitted, uses C<$_>.
=item readpipe EXPR
+
+=item readpipe
X<readpipe>
EXPR is executed as a system command.
This is the internal function implementing the C<qx/EXPR/>
operator, but you can use it directly. The C<qx/EXPR/>
operator is discussed in more detail in L<perlop/"I/O Operators">.
+If EXPR is omitted, uses C<$_>.
=item recv SOCKET,SCALAR,LENGTH,FLAGS
X<recv>
print "r is not a reference at all.\n";
}
+The return value C<LVALUE> indicates a reference to an lvalue that is not
+a variable. You get this from taking the reference of function calls like
+C<pos()> or C<substr()>. C<VSTRING> is returned if the reference points
+to a L<version string|perldata\"Version Strings">.
+
+The result C<Regexp> indicates that the argument is a regular expression
+resulting from C<qr//>.
+
See also L<perlref>.
=item rename OLDNAME,NEWNAME
Otherwise, C<require> demands that a library file be included if it
hasn't already been included. The file is included via the do-FILE
-mechanism, which is essentially just a variety of C<eval>. Has
-semantics similar to the following subroutine:
+mechanism, which is essentially just a variety of C<eval> with the
+caveat that lexical variables in the invoking script will be invisible
+to the included code. Has semantics similar to the following subroutine:
sub require {
my ($filename) = @_;
=item say
Just like C<print>, but implicitly appends a newline.
-C<say LIST> is simply an abbreviation for C<{ local $/ = "\n"; print
+C<say LIST> is simply an abbreviation for C<{ local $\ = "\n"; print
LIST }>.
This keyword is only available when the "say" feature is
=item select
-Returns the currently selected filehandle. Sets the current default
-filehandle for output, if FILEHANDLE is supplied. This has two
+Returns the currently selected filehandle. If FILEHANDLE is supplied,
+sets the new current default filehandle for output. This has two
effects: first, a C<write> or a C<print> without a filehandle will
default to this FILEHANDLE. Second, references to variables related to
output will refer to this output channel. For example, if you have to
=item state TYPE EXPR : ATTRS
C<state> declares a lexically scoped variable, just like C<my> does.
-However, those variables will be initialized only once, contrary to
+However, those variables will never be reinitialized, contrary to
lexical variables that are reinitialized each time their enclosing block
is entered.
except that Module I<must> be a bareword.
-VERSION may be either a numeric argument such as 5.006, which will be
-compared to C<$]>, or a literal of the form v5.6.1, which will be compared
-to C<$^V> (aka $PERL_VERSION. A fatal error is produced if VERSION is
-greater than the version of the current Perl interpreter; Perl will not
-attempt to parse the rest of the file. Compare with L</require>, which can
-do a similar check at run time.
+In the peculiar C<use VERSION> form, VERSION may be either a numeric
+argument such as 5.006, which will be compared to C<$]>, or a literal of
+the form v5.6.1, which will be compared to C<$^V> (aka $PERL_VERSION). A
+fatal error is produced if VERSION is greater than the version of the
+current Perl interpreter; Perl will not attempt to parse the rest of the
+file. Compare with L</require>, which can do a similar check at run time.
+Symmetrically, C<no VERSION> allows you to specify that you want a version
+of perl older than the specified one.
Specifying VERSION as a literal of the form v5.6.1 should generally be
avoided, because it leads to misleading error messages under earlier
C<use>ing library modules that have changed in incompatible ways from
older versions of Perl. (We try not to do this more than we have to.)
+Also, if the specified perl version is greater than or equal to 5.9.5,
+C<use VERSION> will also load the C<feature> pragma and enable all
+features available in the requested version. See L<feature>.
+
The C<BEGIN> forces the C<require> and C<import> to happen at compile time. The
C<require> makes sure the module is loaded into memory if it hasn't been
yet. The C<import> is not a builtin--it's just an ordinary static method
extend the string with sufficiently many zero bytes. It is an error
to try to write off the beginning of the string (i.e. negative OFFSET).
-The string should not contain any character with the value > 255 (which
-can only happen if you're using UTF-8 encoding). If it does, it will be
-treated as something that is not UTF-8 encoded. When the C<vec> was
-assigned to, other parts of your program will also no longer consider the
-string to be UTF-8 encoded. In other words, if you do have such characters
-in your string, vec() will operate on the actual byte string, and not the
-conceptual character string.
+If the string happens to be encoded as UTF-8 internally (and thus has
+the UTF8 flag set), this is ignored by C<vec>, and it operates on the
+internal byte string, not the conceptual character string, even if you
+only have characters with values less than 256.
Strings created with C<vec> can also be manipulated with the logical
operators C<|>, C<&>, C<^>, and C<~>. These operators will assume a bit
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