=over 6
-=item fork()
+=item *
+
+fork()
+
+=item *
-=item some features of the UNIX filesystem regarding link count and file dates
+some features of the UNIX filesystem regarding link count and file dates
-=item inplace operation (the -i switch) without backup file
+=item *
+
+inplace operation (the B<-i> switch) without backup file
+
+=item *
-=item umask() works, but the correct permissions are only set when the file is
- finally close()d
+umask() works, but the correct permissions are only set when the file is
+finally close()d
=back
=over 4
-=item 1. Use another name for the argument, if one is available. For
-example, -value is an alias for -values.
+=item 1.
+
+Use another name for the argument, if one is available.
+For example, -value is an alias for -values.
-=item 2. Change the capitalization, e.g. -Values
+=item 2.
-=item 3. Put quotes around the argument name, e.g. '-values'
+Change the capitalization, e.g. -Values
+
+=item 3.
+
+Put quotes around the argument name, e.g. '-values'
=back
The second argument (-src) is also required and specifies the URL
=item 3.
+
The third option (-align, optional) is an alignment type, and may be
TOP, BOTTOM or MIDDLE
if the former is unavailable.
=item B<script_name()>
+
Return the script name as a partial URL, for self-refering
scripts.
CGI->nph(1)
-=item By using B<-nph> parameters in the B<header()> and B<redirect()> statements:
+=item By using B<-nph> parameters
+
+in the B<header()> and B<redirect()> statements:
print $q->header(-nph=>1);
Returns the author's ID of the module.
-=item
-
=back
=head2 Cache Manager
=over
-=item 1) I installed a new version of module X but CPAN keeps saying,
- I have the old version installed
+=item 1)
+
+I installed a new version of module X but CPAN keeps saying,
+I have the old version installed
Most probably you B<do> have the old version installed. This can
happen if a module installs itself into a different directory in the
o conf make_install_arg UNINST=1
-=item 2) So why is UNINST=1 not the default?
+=item 2)
+
+So why is UNINST=1 not the default?
Because there are people who have their precise expectations about who
may install where in the @INC path and who uses which @INC array. In
fine tuned environments C<UNINST=1> can cause damage.
-=item 3) I want to clean up my mess, and install a new perl along with
- all modules I have. How do I go about it?
+=item 3)
+
+I want to clean up my mess, and install a new perl along with
+all modules I have. How do I go about it?
Run the autobundle command for your old perl and optionally rename the
resulting bundle file (e.g. Bundle/mybundle.pm), install the new perl
and you're done.
-=item 4) When I install bundles or multiple modules with one command
- there is too much output to keep track of
+=item 4)
+
+When I install bundles or multiple modules with one command
+there is too much output to keep track of.
You may want to configure something like
so that STDOUT is captured in a file for later inspection.
-=item 5) I am not root, how can I install a module in a personal
- directory?
+=item 5)
+
+I am not root, how can I install a module in a personal directory?
You will most probably like something like this:
Another thing you should bear in mind is that the UNINST parameter
should never be set if you are not root.
-=item 6) How to get a package, unwrap it, and make a change before
- building it?
+=item 6)
+
+How to get a package, unwrap it, and make a change before building it?
look Sybase::Sybperl
-=item 7) I installed a Bundle and had a couple of fails. When I
- retried, everything resolved nicely. Can this be fixed to work
- on first try?
+=item 7)
+
+I installed a Bundle and had a couple of fails. When I
+retried, everything resolved nicely. Can this be fixed to work
+on first try?
The reason for this is that CPAN does not know the dependencies of all
modules when it starts out. To decide about the additional items to
situation for dependencies on CPAN in general, but this will still
take some time.
-=item 8) In our intranet we have many modules for internal use. How
- can I integrate these modules with CPAN.pm but without uploading
- the modules to CPAN?
+=item 8)
+
+In our intranet we have many modules for internal use. How
+can I integrate these modules with CPAN.pm but without uploading
+the modules to CPAN?
Have a look at the CPAN::Site module.
-=item 9) When I run CPAN's shell, I get error msg about line 1 to 4,
- setting meta input/output via the /etc/inputrc file.
+=item 9)
+
+When I run CPAN's shell, I get error msg about line 1 to 4,
+setting meta input/output via the /etc/inputrc file.
Some versions of readline are picky about capitalization in the
/etc/inputrc file and specifically RedHat 6.2 comes with a
/etc/inputrc that contains the word C<on> in lowercase. Change the
occurrences of C<on> to C<On> and the bug should disappear.
-=item 10) Some authors have strange characters in their names.
+=item 10)
+
+Some authors have strange characters in their names.
Internally CPAN.pm uses the UTF-8 charset. If your terminal is
expecting ISO-8859-1 charset, a converter can be activated by setting
=over 4
-=item
+=item *
+
Match the C<NAME> and C<SYNOPSIS> sections and all of their subsections:
C<NAME|SYNOPSIS>
-=item
+=item *
+
Match only the C<Question> and C<Answer> subsections of the C<DESCRIPTION>
section:
C<DESCRIPTION/Question|Answer>
-=item
+=item *
+
Match the C<Comments> subsection of I<all> sections:
C</Comments>
-=item
+=item *
+
Match all subsections of C<DESCRIPTION> I<except> for C<Comments>:
C<DESCRIPTION/!Comments>
-=item
+=item *
+
Match the C<DESCRIPTION> section but do I<not> match any of its subsections:
C<DESCRIPTION/!.+>
-=item
+=item *
+
Match all top level sections but none of their subsections:
C</!.+>
=over 4
=item 0
+
a simple word
=item 1
+
multiple spaces are skipped because of our $delim
=item 2
+
use of quotes to include a space in a word
=item 3
+
use of a backslash to include a space in a word
=item 4
+
use of a backslash to remove the special meaning of a double-quote
=item 5
+
another simple word (note the lack of effect of the
backslashed double-quote)
system boot. Resolution is limited to system timer ticks (about 10ms
on WinNT and 55ms on Win9X).
-=item Win32::InitiateSystemShutdown(MACHINE, MESSAGE, TIMEOUT, FORCECLOSE, REBOOT)
+=item Win32::InitiateSystemShutdown
+
+(MACHINE, MESSAGE, TIMEOUT, FORCECLOSE, REBOOT)
[EXT] Shutsdown the specified MACHINE, notifying users with the
supplied MESSAGE, within the specified TIMEOUT interval. Forces
=over 4
-=item * modularity and reusability using innumerable modules
+=item *
+
+modularity and reusability using innumerable modules
Described in L<perlmod>, L<perlmodlib>, and L<perlmodinstall>.
-=item * embeddable and extensible
+=item *
+
+embeddable and extensible
Described in L<perlembed>, L<perlxstut>, L<perlxs>, L<perlcall>,
L<perlguts>, and L<xsubpp>.
-=item * roll-your-own magic variables (including multiple simultaneous DBM implementations)
+=item *
+
+roll-your-own magic variables (including multiple simultaneous DBM implementations)
Described in L<perltie> and L<AnyDBM_File>.
-=item * subroutines can now be overridden, autoloaded, and prototyped
+=item *
+
+subroutines can now be overridden, autoloaded, and prototyped
Described in L<perlsub>.
-=item * arbitrarily nested data structures and anonymous functions
+=item *
+
+arbitrarily nested data structures and anonymous functions
Described in L<perlreftut>, L<perlref>, L<perldsc>, and L<perllol>.
-=item * object-oriented programming
+=item *
+
+object-oriented programming
Described in L<perlobj>, L<perltoot>, and L<perlbot>.
-=item * compilability into C code or Perl bytecode
+=item *
+
+compilability into C code or Perl bytecode
Described in L<B> and L<B::Bytecode>.
-=item * support for light-weight processes (threads)
+=item *
+
+support for light-weight processes (threads)
Described in L<perlthrtut> and L<Thread>.
-=item * support for internationalization, localization, and Unicode
+=item *
+
+support for internationalization, localization, and Unicode
Described in L<perllocale> and L<utf8>.
-=item * lexical scoping
+=item *
+
+lexical scoping
Described in L<perlsub>.
-=item * regular expression enhancements
+=item *
+
+regular expression enhancements
Described in L<perlre>, with additional examples in L<perlop>.
-=item * enhanced debugger and interactive Perl environment, with integrated editor support
+=item *
+
+enhanced debugger and interactive Perl environment,
+with integrated editor support
Described in L<perldebug>.
-=item * POSIX 1003.1 compliant library
+=item *
+
+POSIX 1003.1 compliant library
Described in L<POSIX>.
like a list when you assign to it, and provides a list context to its
subscript, which can do weird things if you're expecting only one subscript.
-=item Stub found while resolving method `%s' overloading `%s' in package `%s'
+=item Stub found while resolving method `%s' overloading `%s' in %s
(P) Overloading resolution over @ISA tree may be broken by importing stubs.
Stubs should never be implicitly created, but explicit calls to C<can>
=over 4
-=item Core sources now require ANSI C compiler
+=item *
+
+Core sources now require ANSI C compiler
An ANSI C compiler is now B<required> to build perl. See F<INSTALL>.
-=item All Perl global variables must now be referenced with an explicit prefix
+=item *
+
+All Perl global variables must now be referenced with an explicit prefix
All Perl global variables that are visible for use by extensions now
have a C<PL_> prefix. New extensions should C<not> refer to perl globals
See L<perlguts/"API LISTING">.
-=item Enabling threads has source compatibility issues
+=item *
+
+Enabling threads has source compatibility issues
Perl built with threading enabled requires extensions to use the new
C<dTHR> macro to initialize the handle to access per-thread data.
One possible workaround is to force Perl to use magical string
increment by prepending "0" to your numbers.
-=item Recursive inheritance detected while looking for method '%s' in package '%s'
+=item Recursive inheritance detected while looking for method '%s' %s
(F) More than 100 levels of inheritance were encountered while invoking a
method. Probably indicates an unintended loop in your inheritance hierarchy.
The C<flags> value will normally be zero; if set to G_DISCARD then NULL
will be returned.
- SV* hv_delete(HV* tb, const char* key, U32 klen, I32 flags)
+ SV* hv_delete(HV* tb, const char* key, I32 klen, I32 flags)
=for hackers
Found in file hv.c
Returns a boolean indicating whether the specified hash key exists. The
C<klen> is the length of the key.
- bool hv_exists(HV* tb, const char* key, U32 klen)
+ bool hv_exists(HV* tb, const char* key, I32 klen)
=for hackers
Found in file hv.c
See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.
- SV** hv_fetch(HV* tb, const char* key, U32 klen, I32 lval)
+ SV** hv_fetch(HV* tb, const char* key, I32 klen, I32 lval)
=for hackers
Found in file hv.c
See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.
- SV** hv_store(HV* tb, const char* key, U32 klen, SV* val, U32 hash)
+ SV** hv_store(HV* tb, const char* key, I32 klen, SV* val, U32 hash)
=for hackers
Found in file hv.c
In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">.
-=item delete(), values() and C<\(%h)> operate on aliases to values, not copies
+=item delete(), each(), values() and C<\(%h)>
-delete(), each(), values() and hashes in a list context return the actual
+operate on aliases to values, not copies
+
+delete(), each(), values() and hashes (e.g. C<\(%h)>)
+in a list context return the actual
values in the hash, instead of copies (as they used to in earlier
versions). Typical idioms for using these constructs copy the
returned values, but this can make a significant difference when
=item The DB module
-=item The regular expression constructs C<(?{ code })> and C<(??{ code })>
+=item The regular expression code constructs:
+
+C<(?{ code })> and C<(??{ code })>
=back
to check the return value of your socket() call? See
L<perlfunc/listen>.
-=item Lookbehind longer than %d not implemented at {#} mark in regex 5s
+=item Lookbehind longer than %d not implemented at {#} mark in regex %s
There is an upper limit to the depth of lookbehind in the (?<=
regular expression construct.
values cannot be returned in subroutines used in lvalue context. See
L<perlsub/"Lvalue subroutines">.
-=item Lookbehind longer than %d not implemented before << HERE in reges m/%s/
+=item Lookbehind longer than %d not implemented before << HERE %s
(F) There is currently a limit on the length of string which lookbehind can
handle. This restriction may be eased in a future release. The << HERE shows in
{min,max} construct. The << HERE shows in the regular expression about where
the problem was discovered. See L<perlre>.
-=item Quantifier unexpected on zero-length expression before << HERE in regex m/%s/
+=item Quantifier unexpected on zero-length expression before << HERE %s
(W regexp) You applied a regular expression quantifier in a place where
it makes no sense, such as on a zero-width assertion. Try putting the
shows in the regular expression about where the problem was discovered. See
L<perlre>.
-=item Sequence (?{...}) not terminated or not {}-balanced in regex m/%s/
+=item Sequence (?{...}) not terminated or not {}-balanced in %s
(F) If the contents of a (?{...}) clause contains braces, they must balance
for Perl to properly detect the end of the clause. See L<perlre>.
-=item Sequence (?%s...) not implemented before << HERE mark in regex m/%s/
+=item Sequence (?%s...) not implemented before << HERE mark in %s
(F) A proposed regular expression extension has the character reserved but
has not yet been written. The << HERE shows in the regular expression about
where the problem was discovered. See L<perlre>.
-=item Sequence (?%s...) not recognized before << HERE mark in regex m/%s/
+=item Sequence (?%s...) not recognized before << HERE mark in %s
(F) You used a regular expression extension that doesn't make sense.
The << HERE shows in the regular expression about
(F) Your Perl was compiled with B<-D>SETUID_SCRIPTS_ARE_SECURE_NOW, but
a version of the setuid emulator somehow got run anyway.
-=item Switch (?(condition)... contains too many branches before << HERE in regex m/%s/
+=item Switch (?(condition)... contains too many branches before << HE%s
(F) A (?(condition)if-clause|else-clause) construct can have at most two
branches (the if-clause and the else-clause). If you want one or both to
reference variables in outer subroutines are called or referenced, they
are automatically rebound to the current values of such variables.
-=item Variable length lookbehind not implemented before << HERE in regex m/%s/
+=item Variable length lookbehind not implemented before << HERE in %s
(F) Lookbehind is allowed only for subexpressions whose length is fixed and
known at compile time. The << HERE shows in the regular expression about where
=over 5
-=item Compiling your C program
+=item *
-=item Adding a Perl interpreter to your C program
+Compiling your C program
-=item Calling a Perl subroutine from your C program
+=item *
-=item Evaluating a Perl statement from your C program
+Adding a Perl interpreter to your C program
-=item Performing Perl pattern matches and substitutions from your C program
+=item *
-=item Fiddling with the Perl stack from your C program
+Calling a Perl subroutine from your C program
-=item Maintaining a persistent interpreter
+=item *
-=item Maintaining multiple interpreter instances
+Evaluating a Perl statement from your C program
-=item Using Perl modules, which themselves use C libraries, from your C program
+=item *
-=item Embedding Perl under Win32
+Performing Perl pattern matches and substitutions from your C program
+
+=item *
+
+Fiddling with the Perl stack from your C program
+
+=item *
+
+Maintaining a persistent interpreter
+
+=item *
+
+Maintaining multiple interpreter instances
+
+=item *
+
+Using Perl modules, which themselves use C libraries, from your C program
+
+=item *
+
+Embedding Perl under Win32
=back
=over 4
-=item a) If @in is sorted, and you want @out to be sorted:
+=item a)
+
+If @in is sorted, and you want @out to be sorted:
(this assumes all true values in the array)
$prev = 'nonesuch';
guarantees that the expression is true (so that grep picks it up)
even if the $_ is 0, "", or undef.
-=item b) If you don't know whether @in is sorted:
+=item b)
+
+If you don't know whether @in is sorted:
undef %saw;
@out = grep(!$saw{$_}++, @in);
-=item c) Like (b), but @in contains only small integers:
+=item c)
+
+Like (b), but @in contains only small integers:
@out = grep(!$saw[$_]++, @in);
-=item d) A way to do (b) without any loops or greps:
+=item d)
+
+A way to do (b) without any loops or greps:
undef %saw;
@saw{@in} = ();
@out = sort keys %saw; # remove sort if undesired
-=item e) Like (d), but @in contains only small positive integers:
+=item e)
+
+Like (d), but @in contains only small positive integers:
undef @ary;
@ary[@in] = @in;
=over 4
-=item B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
+=item *
+
+B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
Scalar true/false (or less/equal/greater) result is never tainted.
-=item B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or C<\U>)
+=item *
+
+B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or C<\U>)
Result string containing interpolated material is tainted if
C<use locale> is in effect.
-=item B<Matching operator> (C<m//>):
+=item *
+
+B<Matching operator> (C<m//>):
Scalar true/false result never tainted.
C<use locale> is in effect and the regular expression contains C<\w>,
C<\W>, C<\s>, or C<\S>.
-=item B<Substitution operator> (C<s///>):
+=item *
+
+B<Substitution operator> (C<s///>):
Has the same behavior as the match operator. Also, the left
operand of C<=~> becomes tainted when C<use locale> in effect
expression match involving C<\w>, C<\W>, C<\s>, or C<\S>; or of
case-mapping with C<\l>, C<\L>,C<\u> or C<\U>.
-=item B<Output formatting functions> (printf() and write()):
+=item *
+
+B<Output formatting functions> (printf() and write()):
Success/failure result is never tainted.
-=item B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()):
+=item *
+
+B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()):
Results are tainted if C<use locale> is in effect.
-=item B<POSIX locale-dependent functions> (localeconv(), strcoll(),
+=item *
+
+B<POSIX locale-dependent functions> (localeconv(), strcoll(),
strftime(), strxfrm()):
Results are never tainted.
-=item B<POSIX character class tests> (isalnum(), isalpha(), isdigit(),
+=item *
+
+B<POSIX character class tests> (isalnum(), isalpha(), isdigit(),
isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(),
isxdigit()):
=over 4
=item *
+
Language Extensions and Documentation Tools
=item *
+
Development Support
=item *
+
Operating System Interfaces
=item *
+
Networking, Device Control (modems) and InterProcess Communication
=item *
+
Data Types and Data Type Utilities
=item *
+
Database Interfaces
=item *
+
User Interfaces
=item *
+
Interfaces to / Emulations of Other Programming Languages
=item *
+
File Names, File Systems and File Locking (see also File Handles)
=item *
+
String Processing, Language Text Processing, Parsing, and Searching
=item *
+
Option, Argument, Parameter, and Configuration File Processing
=item *
+
Internationalization and Locale
=item *
+
Authentication, Security, and Encryption
=item *
+
World Wide Web, HTML, HTTP, CGI, MIME
=item *
+
Server and Daemon Utilities
=item *
+
Archiving and Compression
=item *
+
Images, Pixmap and Bitmap Manipulation, Drawing, and Graphing
=item *
+
Mail and Usenet News
=item *
+
Control Flow Utilities (callbacks and exceptions etc)
=item *
+
File Handle and Input/Output Stream Utilities
=item *
+
Miscellaneous Modules
=back
=over 4
-=item Complete applications rarely belong in the Perl Module Library.
+=item *
+
+Complete applications rarely belong in the Perl Module Library.
-=item Many applications contain some Perl code that could be reused.
+=item *
+
+Many applications contain some Perl code that could be reused.
Help save the world! Share your code in a form that makes it easy
to reuse.
-=item Break-out the reusable code into one or more separate module files.
+=item *
+
+Break-out the reusable code into one or more separate module files.
-=item Take the opportunity to reconsider and redesign the interfaces.
+=item *
+
+Take the opportunity to reconsider and redesign the interfaces.
+
+=item *
-=item In some cases the 'application' can then be reduced to a small
+In some cases the 'application' can then be reduced to a small
fragment of code built on top of the reusable modules. In these cases
the application could invoked as:
=over 4
=item *
+
\d is a digit and represents [0-9]
=item *
+
\s is a whitespace character and represents [\ \t\r\n\f]
=item *
+
\w is a word character (alphanumeric or _) and represents [0-9a-zA-Z_]
=item *
+
\D is a negated \d; it represents any character but a digit [^0-9]
=item *
+
\S is a negated \s; it represents any non-whitespace character [^\s]
=item *
+
\W is a negated \w; it represents any non-word character [^\w]
=item *
+
The period '.' matches any character but "\n"
=back
=over 4
-=item * C<a?> = match 'a' 1 or 0 times
+=item *
-=item * C<a*> = match 'a' 0 or more times, i.e., any number of times
+C<a?> = match 'a' 1 or 0 times
+
+=item *
-=item * C<a+> = match 'a' 1 or more times, i.e., at least once
+C<a*> = match 'a' 0 or more times, i.e., any number of times
-=item * C<a{n,m}> = match at least C<n> times, but not more than C<m>
+=item *
+
+C<a+> = match 'a' 1 or more times, i.e., at least once
+
+=item *
+
+C<a{n,m}> = match at least C<n> times, but not more than C<m>
times.
-=item * C<a{n,}> = match at least C<n> or more times
+=item *
+
+C<a{n,}> = match at least C<n> or more times
+
+=item *
-
=item * C<a{n}> = match exactly C<n> times
+C<a{n}> = match exactly C<n> times
=back
=over 4
=item *
+
\d is a digit and represents [0-9]
=item *
+
\s is a whitespace character and represents [\ \t\r\n\f]
=item *
+
\w is a word character (alphanumeric or _) and represents [0-9a-zA-Z_]
=item *
+
\D is a negated \d; it represents any character but a digit [^0-9]
=item *
+
\S is a negated \s; it represents any non-whitespace character [^\s]
=item *
+
\W is a negated \w; it represents any non-word character [^\w]
=item *
+
The period '.' matches any character but "\n"
=back
=over 4
=item *
+
no modifiers (//): Default behavior. C<'.'> matches any character
except C<"\n">. C<^> matches only at the beginning of the string and
C<$> matches only at the end or before a newline at the end.
=item *
+
s modifier (//s): Treat string as a single long line. C<'.'> matches
any character, even C<"\n">. C<^> matches only at the beginning of
the string and C<$> matches only at the end or before a newline at the
end.
=item *
+
m modifier (//m): Treat string as a set of multiple lines. C<'.'>
matches any character except C<"\n">. C<^> and C<$> are able to match
at the start or end of I<any> line within the string.
=item *
+
both s and m modifiers (//sm): Treat string as a single long line, but
detect multiple lines. C<'.'> matches any character, even
C<"\n">. C<^> and C<$>, however, are able to match at the start or end
=over 4
-=item 0 Start with the first letter in the string 'a'.
+=item 0
+
+Start with the first letter in the string 'a'.
+
+=item 1
-=item 1 Try the first alternative in the first group 'abd'.
+Try the first alternative in the first group 'abd'.
-=item 2 Match 'a' followed by 'b'. So far so good.
+=item 2
-=item 3 'd' in the regexp doesn't match 'c' in the string - a dead
+Match 'a' followed by 'b'. So far so good.
+
+=item 3
+
+'d' in the regexp doesn't match 'c' in the string - a dead
end. So backtrack two characters and pick the second alternative in
the first group 'abc'.
-=item 4 Match 'a' followed by 'b' followed by 'c'. We are on a roll
+=item 4
+
+Match 'a' followed by 'b' followed by 'c'. We are on a roll
and have satisfied the first group. Set $1 to 'abc'.
-=item 5 Move on to the second group and pick the first alternative
+=item 5
+
+Move on to the second group and pick the first alternative
'df'.
-=item 6 Match the 'd'.
+=item 6
-=item 7 'f' in the regexp doesn't match 'e' in the string, so a dead
+Match the 'd'.
+
+=item 7
+
+'f' in the regexp doesn't match 'e' in the string, so a dead
end. Backtrack one character and pick the second alternative in the
second group 'd'.
-=item 8 'd' matches. The second grouping is satisfied, so set $2 to
+=item 8
+
+'d' matches. The second grouping is satisfied, so set $2 to
'd'.
-=item 9 We are at the end of the regexp, so we are done! We have
+=item 9
+
+We are at the end of the regexp, so we are done! We have
matched 'abcd' out of the string "abcde".
=back
=over 4
-=item * C<a?> = match 'a' 1 or 0 times
+=item *
-=item * C<a*> = match 'a' 0 or more times, i.e., any number of times
+C<a?> = match 'a' 1 or 0 times
-=item * C<a+> = match 'a' 1 or more times, i.e., at least once
+=item *
+
+C<a*> = match 'a' 0 or more times, i.e., any number of times
+
+=item *
-=item * C<a{n,m}> = match at least C<n> times, but not more than C<m>
+C<a+> = match 'a' 1 or more times, i.e., at least once
+
+=item *
+
+C<a{n,m}> = match at least C<n> times, but not more than C<m>
times.
-=item * C<a{n,}> = match at least C<n> or more times
+=item *
+
+C<a{n,}> = match at least C<n> or more times
+
+=item *
-
=item * C<a{n}> = match exactly C<n> times
+C<a{n}> = match exactly C<n> times
=back
=over 4
=item *
+
Principle 0: Taken as a whole, any regexp will be matched at the
earliest possible position in the string.
=item *
+
Principle 1: In an alternation C<a|b|c...>, the leftmost alternative
that allows a match for the whole regexp will be the one used.
=item *
+
Principle 2: The maximal matching quantifiers C<?>, C<*>, C<+> and
C<{n,m}> will in general match as much of the string as possible while
still allowing the whole regexp to match.
=item *
+
Principle 3: If there are two or more elements in a regexp, the
leftmost greedy quantifier, if any, will match as much of the string
as possible while still allowing the whole regexp to match. The next
=over 4
-=item * C<a??> = match 'a' 0 or 1 times. Try 0 first, then 1.
+=item *
+
+C<a??> = match 'a' 0 or 1 times. Try 0 first, then 1.
-=item * C<a*?> = match 'a' 0 or more times, i.e., any number of times,
+=item *
+
+C<a*?> = match 'a' 0 or more times, i.e., any number of times,
but as few times as possible
-=item * C<a+?> = match 'a' 1 or more times, i.e., at least once, but
+=item *
+
+C<a+?> = match 'a' 1 or more times, i.e., at least once, but
as few times as possible
-=item * C<a{n,m}?> = match at least C<n> times, not more than C<m>
+=item *
+
+C<a{n,m}?> = match at least C<n> times, not more than C<m>
times, as few times as possible
-=item * C<a{n,}?> = match at least C<n> times, but as few times as
+=item *
+
+C<a{n,}?> = match at least C<n> times, but as few times as
possible
-=item * C<a{n}?> = match exactly C<n> times. Because we match exactly
+=item *
+
+C<a{n}?> = match exactly C<n> times. Because we match exactly
C<n> times, C<a{n}?> is equivalent to C<a{n}> and is just there for
notational consistency.
=over 4
=item *
+
Principle 3: If there are two or more elements in a regexp, the
leftmost greedy (non-greedy) quantifier, if any, will match as much
(little) of the string as possible while still allowing the whole
=over 4
-=item 0 Start with the first letter in the string 't'.
+=item 0
+
+Start with the first letter in the string 't'.
-=item 1 The first quantifier '.*' starts out by matching the whole
+=item 1
+
+The first quantifier '.*' starts out by matching the whole
string 'the cat in the hat'.
-=item 2 'a' in the regexp element 'at' doesn't match the end of the
+=item 2
+
+'a' in the regexp element 'at' doesn't match the end of the
string. Backtrack one character.
-=item 3 'a' in the regexp element 'at' still doesn't match the last
+=item 3
+
+'a' in the regexp element 'at' still doesn't match the last
letter of the string 't', so backtrack one more character.
-=item 4 Now we can match the 'a' and the 't'.
+=item 4
+
+Now we can match the 'a' and the 't'.
-=item 5 Move on to the third element '.*'. Since we are at the end of
+=item 5
+
+Move on to the third element '.*'. Since we are at the end of
the string and '.*' can match 0 times, assign it the empty string.
-=item 6 We are done!
+=item 6
+
+We are done!
=back
=over 4
-=item * specifying the task in detail,
+=item *
+
+specifying the task in detail,
-=item * breaking down the problem into smaller parts,
+=item *
+
+breaking down the problem into smaller parts,
+
+=item *
-=item * translating the small parts into regexps,
+translating the small parts into regexps,
-=item * combining the regexps,
+=item *
+
+combining the regexps,
+
+=item *
-=item * and optimizing the final combined regexp.
+and optimizing the final combined regexp.
=back
=over 4
-=item 1. You need to give a global variable a temporary value, especially $_.
+=item 1.
+
+You need to give a global variable a temporary value, especially $_.
The global variables, like C<@ARGV> or the punctuation variables, must be
C<local>ized with C<local()>. This block reads in F</etc/motd>, and splits
It particular, it's important to C<local>ize $_ in any routine that assigns
to it. Look out for implicit assignments in C<while> conditionals.
-=item 2. You need to create a local file or directory handle or a local function.
+=item 2.
+
+You need to create a local file or directory handle or a local function.
A function that needs a filehandle of its own must use
C<local()> on a complete typeglob. This can be used to create new symbol
See L<perlref/"Function Templates"> for more about manipulating
functions by name in this way.
-=item 3. You want to temporarily change just one element of an array or hash.
+=item 3.
+
+You want to temporarily change just one element of an array or hash.
You can C<local>ize just one element of an aggregate. Usually this
is done on dynamics:
https://perl5.git.perl.org / perl5.git / commitdiff