Regexp::Common(3) User Contributed Perl Documentation Regexp::Common(3)NAMERegexp::Common - Provide commonly requested regular expressions
SYNOPSIS
# STANDARD USAGE
use Regexp::Common;
while (<>) {
/$RE{num}{real}/ and print q{a number};
/$RE{quoted}/ and print q{a ['"`] quoted string};
/$RE{delimited}{-delim=>'/'}/ and print q{a /.../ sequence};
/$RE{balanced}{-parens=>'()'}/ and print q{balanced parentheses};
/$RE{profanity}/ and print q{a #*@%-ing word};
}
# SUBROUTINE-BASED INTERFACE
use Regexp::Common 'RE_ALL';
while (<>) {
$_ =~ RE_num_real() and print q{a number};
$_ =~ RE_quoted() and print q{a ['"`] quoted string};
$_ =~ RE_delimited(-delim=>'/') and print q{a /.../ sequence};
$_ =~ RE_balanced(-parens=>'()'} and print q{balanced parentheses};
$_ =~ RE_profanity() and print q{a #*@%-ing word};
}
# IN-LINE MATCHING...
if ( $RE{num}{int}->matches($text) ) {...}
# ...AND SUBSTITUTION
my $cropped = $RE{ws}{crop}->subs($uncropped);
# ROLL-YOUR-OWN PATTERNS
use Regexp::Common 'pattern';
pattern name => ['name', 'mine'],
create => '(?i:J[.]?\s+A[.]?\s+Perl-Hacker)',
;
my $name_matcher = $RE{name}{mine};
pattern name => [ 'lineof', '-char=_' ],
create => sub {
my $flags = shift;
my $char = quotemeta $flags->{-char};
return '(?:^$char+$)';
},
match => sub {
my ($self, $str) = @_;
return $str !~ /[^$self->{flags}{-char}]/;
},
subs => sub {
my ($self, $str, $replacement) = @_;
$_[1] =~ s/^$self->{flags}{-char}+$//g;
},
;
my $asterisks = $RE{lineof}{-char=>'*'};
# DECIDING WHICH PATTERNS TO LOAD.
use Regexp::Common qw /comment number/; # Comment and number patterns.
use Regexp::Common qw /no_defaults/; # Don't load any patterns.
use Regexp::Common qw /!delimited/; # All, but delimited patterns.
DESCRIPTION
By default, this module exports a single hash (%RE) that stores or
generates commonly needed regular expressions (see "List of available
patterns").
There is an alternative, subroutine-based syntax described in
"Subroutine-based interface".
General syntax for requesting patterns
To access a particular pattern, %RE is treated as a hierarchical hash
of hashes (of hashes...), with each successive key being an identifier.
For example, to access the pattern that matches real numbers, you
specify:
$RE{num}{real}
and to access the pattern that matches integers:
$RE{num}{int}
Deeper layers of the hash are used to specify flags: arguments that
modify the resulting pattern in some way. The keys used to access these
layers are prefixed with a minus sign and may have a value; if a value
is given, it's done by using a multidimensional key. For example, to
access the pattern that matches base-2 real numbers with embedded
commas separating groups of three digits (e.g. 10,101,110.110101101):
$RE{num}{real}{-base => 2}{-sep => ','}{-group => 3}
Through the magic of Perl, these flag layers may be specified in any
order (and even interspersed through the identifier keys!) so you
could get the same pattern with:
$RE{num}{real}{-sep => ','}{-group => 3}{-base => 2}
or:
$RE{num}{-base => 2}{real}{-group => 3}{-sep => ','}
or even:
$RE{-base => 2}{-group => 3}{-sep => ','}{num}{real}
etc.
Note, however, that the relative order of amongst the identifier keys
is significant. That is:
$RE{list}{set}
would not be the same as:
$RE{set}{list}
Flag syntax
In versions prior to 2.113, flags could also be written as
"{"-flag=value"}". This no longer works, although "{"-flag$;value"}"
still does. However, "{-flag => 'value'}" is the preferred syntax.
Universal flags
Normally, flags are specific to a single pattern. However, there is
two flags that all patterns may specify.
"-keep"
By default, the patterns provided by %RE contain no capturing
parentheses. However, if the "-keep" flag is specified (it requires
no value) then any significant substrings that the pattern matches
are captured. For example:
if ($str =~ $RE{num}{real}{-keep}) {
$number = $1;
$whole = $3;
$decimals = $5;
}
Special care is needed if a "kept" pattern is interpolated into a
larger regular expression, as the presence of other capturing
parentheses is likely to change the "number variables" into which
significant substrings are saved.
See also "Adding new regular expressions", which describes how to
create new patterns with "optional" capturing brackets that respond
to "-keep".
"-i"
Some patterns or subpatterns only match lowercase or uppercase
letters. If one wants the do case insensitive matching, one option
is to use the "/i" regexp modifier, or the special sequence "(?i)".
But if the functional interface is used, one does not have this
option. The "-i" switch solves this problem; by using it, the
pattern will do case insensitive matching.
OO interface and inline matching/substitution
The patterns returned from %RE are objects, so rather than writing:
if ($str =~ /$RE{some}{pattern}/ ) {...}
you can write:
if ( $RE{some}{pattern}->matches($str) ) {...}
For matching this would seem to have no great advantage apart from
readability (but see below).
For substitutions, it has other significant benefits. Frequently you
want to perform a substitution on a string without changing the
original. Most people use this:
$changed = $original;
$changed =~ s/$RE{some}{pattern}/$replacement/;
The more adept use:
($changed = $original) =~ s/$RE{some}{pattern}/$replacement/;
Regexp::Common allows you do write this:
$changed = $RE{some}{pattern}->subs($original=>$replacement);
Apart from reducing precedence-angst, this approach has the added
advantages that the substitution behaviour can be optimized from the
regular expression, and the replacement string can be provided by
default (see "Adding new regular expressions").
For example, in the implementation of this substitution:
$cropped = $RE{ws}{crop}->subs($uncropped);
the default empty string is provided automatically, and the
substitution is optimized to use:
$uncropped =~ s/^\s+//;
$uncropped =~ s/\s+$//;
rather than:
$uncropped =~ s/^\s+|\s+$//g;
Subroutine-based interface
The hash-based interface was chosen because it allows regexes to be
effortlessly interpolated, and because it also allows them to be
"curried". For example:
my $num = $RE{num}{int};
my $commad = $num->{-sep=>','}{-group=>3};
my $duodecimal = $num->{-base=>12};
However, the use of tied hashes does make the access to Regexp::Common
patterns slower than it might otherwise be. In contexts where
impatience overrules laziness, Regexp::Common provides an additional
subroutine-based interface.
For each (sub-)entry in the %RE hash ($RE{key1}{key2}{etc}), there is a
corresponding exportable subroutine: "RE_key1_key2_etc()". The name of
each subroutine is the underscore-separated concatenation of the non-
flag keys that locate the same pattern in %RE. Flags are passed to the
subroutine in its argument list. Thus:
use Regexp::Common qw( RE_ws_crop RE_num_real RE_profanity );
$str =~ RE_ws_crop() and die "Surrounded by whitespace";
$str =~ RE_num_real(-base=>8, -sep=>" ") or next;
$offensive = RE_profanity(-keep);
$str =~ s/$offensive/$bad{$1}++; "<expletive deleted>"/ge;
Note that, unlike the hash-based interface (which returns objects),
these subroutines return ordinary "qr"'d regular expressions. Hence
they do not curry, nor do they provide the OO match and substitution
inlining described in the previous section.
It is also possible to export subroutines for all available patterns
like so:
use Regexp::Common 'RE_ALL';
Or you can export all subroutines with a common prefix of keys like so:
use Regexp::Common 'RE_num_ALL';
which will export "RE_num_int" and "RE_num_real" (and if you have
create more patterns who have first key num, those will be exported as
well). In general, RE_key1_..._keyn_ALL will export all subroutines
whose pattern names have first keys key1 ... keyn.
Adding new regular expressions
You can add your own regular expressions to the %RE hash at run-time,
using the exportable "pattern" subroutine. It expects a hash-like list
of key/value pairs that specify the behaviour of the pattern. The
various possible argument pairs are:
"name => [ @list ]"
A required argument that specifies the name of the pattern, and any
flags it may take, via a reference to a list of strings. For
example:
pattern name => [qw( line of -char )],
# other args here
;
This specifies an entry $RE{line}{of}, which may take a "-char"
flag.
Flags may also be specified with a default value, which is then
used whenever the flag is specified without an explicit value (but
not when the flag is omitted). For example:
pattern name => [qw( line of -char=_ )],
# default char is '_'
# other args here
;
"create => $sub_ref_or_string"
A required argument that specifies either a string that is to be
returned as the pattern:
pattern name => [qw( line of underscores )],
create => q/(?:^_+$)/
;
or a reference to a subroutine that will be called to create the
pattern:
pattern name => [qw( line of -char=_ )],
create => sub {
my ($self, $flags) = @_;
my $char = quotemeta $flags->{-char};
return '(?:^$char+$)';
},
;
If the subroutine version is used, the subroutine will be called
with three arguments: a reference to the pattern object itself, a
reference to a hash containing the flags and their values, and a
reference to an array containing the non-flag keys.
Whatever the subroutine returns is stringified as the pattern.
No matter how the pattern is created, it is immediately
postprocessed to include or exclude capturing parentheses
(according to the value of the "-keep" flag). To specify such
"optional" capturing parentheses within the regular expression
associated with "create", use the notation "(?k:...)". Any
parentheses of this type will be converted to "(...)" when the
"-keep" flag is specified, or "(?:...)" when it is not. It is a
Regexp::Common convention that the outermost capturing parentheses
always capture the entire pattern, but this is not enforced.
"match => $sub_ref"
An optional argument that specifies a subroutine that is to be
called when the "$RE{...}->matches(...)" method of this pattern is
invoked.
The subroutine should expect two arguments: a reference to the
pattern object itself, and the string to be matched against.
It should return the same types of values as a "m/.../" does.
pattern name => [qw( line of -char )],
create => sub {...},
match => sub {
my ($self, $str) = @_;
$str !~ /[^$self->{flags}{-char}]/;
},
;
"subs => $sub_ref"
An optional argument that specifies a subroutine that is to be
called when the "$RE{...}->subs(...)" method of this pattern is
invoked.
The subroutine should expect three arguments: a reference to the
pattern object itself, the string to be changed, and the value to
be substituted into it. The third argument may be "undef",
indicating the default substitution is required.
The subroutine should return the same types of values as an
"s/.../.../" does.
For example:
pattern name => [ 'lineof', '-char=_' ],
create => sub {...},
subs => sub {
my ($self, $str, $ignore_replacement) = @_;
$_[1] =~ s/^$self->{flags}{-char}+$//g;
},
;
Note that such a subroutine will almost always need to modify $_[1]
directly.
"version => $minimum_perl_version"
If this argument is given, it specifies the minimum version of perl
required to use the new pattern. Attempts to use the pattern with
earlier versions of perl will generate a fatal diagnostic.
Loading specific sets of patterns.
By default, all the sets of patterns listed below are made available.
However, it is possible to indicate which sets of patterns should be
made available - the wanted sets should be given as arguments to "use".
Alternatively, it is also possible to indicate which sets of patterns
should not be made available - those sets will be given as argument to
the "use" statement, but are preceeded with an exclaimation mark. The
argument no_defaults indicates none of the default patterns should be
made available. This is useful for instance if all you want is the
"pattern()" subroutine.
Examples:
use Regexp::Common qw /comment number/; # Comment and number patterns.
use Regexp::Common qw /no_defaults/; # Don't load any patterns.
use Regexp::Common qw /!delimited/; # All, but delimited patterns.
It's also possible to load your own set of patterns. If you have a
module "Regexp::Common::my_patterns" that makes patterns available, you
can have it made available with
use Regexp::Common qw /my_patterns/;
Note that the default patterns will still be made available - only if
you use no_defaults, or mention one of the default sets explicitely,
the non mentioned defaults aren't made available.
List of available patterns
The patterns listed below are currently available. Each set of patterns
has its own manual page describing the details. For each pattern set
named name, the manual page Regexp::Common::name describes the details.
Currently available are:
Regexp::Common::balanced
Provides regexes for strings with balanced parenthesized
delimiters.
Regexp::Common::comment
Provides regexes for comments of various languages (43 languages
currently).
Regexp::Common::delimited
Provides regexes for delimited strings.
Regexp::Common::lingua
Provides regexes for palindromes.
Regexp::Common::list
Provides regexes for lists.
Regexp::Common::net
Provides regexes for IPv4 addresses and MAC addresses.
Regexp::Common::number
Provides regexes for numbers (integers and reals).
Regexp::Common::profanity
Provides regexes for profanity.
Regexp::Common::whitespace
Provides regexes for leading and trailing whitespace.
Regexp::Common::zip
Provides regexes for zip codes.
Forthcoming patterns and features
Future releases of the module will also provide patterns for the
following:
* email addresses
* HTML/XML tags
* more numerical matchers,
* mail headers (including multiline ones),
* more URLS
* telephone numbers of various countries
* currency (universal 3 letter format, Latin-1, currency names)
* dates
* binary formats (e.g. UUencoded, MIMEd)
If you have other patterns or pattern generators that you think would
be generally useful, please send them to the maintainer -- preferably
as source code using the "pattern" subroutine. Submissions that include
a set of tests will be especially welcome.
DIAGNOSTICS
"Can't export unknown subroutine %s"
The subroutine-based interface didn't recognize the requested
subroutine. Often caused by a spelling mistake or an incompletely
specified name.
"Can't create unknown regex: $RE{...}"
Regexp::Common doesn't have a generator for the requested pattern.
Often indicates a mispelt or missing parameter.
"Perl %f does not support the pattern $RE{...}. You need Perl %f or
later"
The requested pattern requires advanced regex features (e.g.
recursion) that not available in your version of Perl. Time to
upgrade.
"pattern() requires argument: name => [ @list ]"
Every user-defined pattern specification must have a name.
"pattern() requires argument: create => $sub_ref_or_string"
Every user-defined pattern specification must provide a pattern
creation mechanism: either a pattern string or a reference to a
subroutine that returns the pattern string.
"Base must be between 1 and 36"
The $RE{num}{real}{-base=>'N'} pattern uses the characters [0-9A-Z]
to represent the digits of various bases. Hence it only produces
regular expressions for bases up to hexatricensimal.
"Must specify delimiter in $RE{delimited}"
The pattern has no default delimiter. You need to write:
$RE{delimited}{-delim=>X'} for some character X
ACKNOWLEDGEMENTS
Deepest thanks to the many people who have encouraged and contributed
to this project, especially: Elijah, Jarkko, Tom, Nat, Ed, and Vivek.
Further thanks go to: Alexandr Ciornii, Blair Zajac, Bob Stockdale,
Charles Thomas, Chris Vertonghen, the CPAN Testers, David Hand, Fany,
Geoffrey Leach, Hermann-Marcus Behrens, Jerome Quelin, Jim Cromie, Lars
Wilke, Linda Julien, Mike Arms, Mike Castle, Mikko, Murat Uenalan,
Rafaeel Garcia-Suarez, Ron Savage, Sam Vilain, Slaven Rezic, Smylers,
Tim Maher, and all the others I've forgotten.
AUTHOR
Damian Conway (damian@conway.org)
MAINTAINANCE
This package is maintained by Abigail (regexp-common@abigail.be).
BUGS AND IRRITATIONS
Bound to be plenty.
For a start, there are many common regexes missing. Send them in to
regexp-common@abigail.be.
There are some POD issues when installing this module using a pre-5.6.0
perl; some manual pages may not install, or may not install correctly
using a perl that is that old. You might consider upgrading your perl.
NOT A BUG
ยท The various patterns are not anchored. That is, a pattern like "$RE
{num} {int}" will match against "abc4def", because a substring of
the subject matches. This is by design, and not a bug. If you want
the pattern to be anchored, use something like:
my $integer = $RE {num} {int};
$subj =~ /^$integer$/ and print "Matches!\n";
LICENSE and COPYRIGHT
This software is Copyright (c) 2001 - 2011, Damian Conway and Abigail.
This module is free software, and maybe used under any of the following
licenses:
1) The Perl Artistic License. See the file COPYRIGHT.AL.
2) The Perl Artistic License 2.0. See the file COPYRIGHT.AL2.
3) The BSD Licence. See the file COPYRIGHT.BSD.
4) The MIT Licence. See the file COPYRIGHT.MIT.
perl v5.14.2 2011-12-10 Regexp::Common(3)
