Regular expression examples: Difference between revisions

Revision as of 14:42, 31 March 2007

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Despite this variability, and because regular expressions can be difficult to both explain and understand without examples, this article provides a basic description of some of the properties of regular expressions by way of illustration.

== Conventions ==

The following conventions are used in the examples.<ref name="clarify000">The character 'm' is not always required to specify a perl match operation. For example, m/[^abc]/ could also be rendered as /[^abc]/. The 'm' is only necessary if the user wishes to specify a match operation without using a forward-slash as the regex [[delimiter]]. Sometimes it is useful to specify an alternate regex delimiter in order to avoid "[[Delimiter#Delimiter_collision|delimiter collision]]". See '[http://perldoc.perl.org/perlre.html perldoc perlre]' for more details.</ref>

=~ m// ;; indicates a regex '''match''' operation in perl

=~ s/// ;; indicates a regex '''substitution''' operation in perl

metacharacter(s) ;; the metacharacters column specifies the regex syntax being demonstrated

== Examples ==

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== Notes ==

<references />

The character 'm' in the above regular expressions, for example m/[^abc]/, is not required in order for perl to recognize the expression as a 'match' (cf. 'substitute': s/a/b/); /[^abc]/ could just as easily be used without the preceding 'm'. The 'm' operator can be used to alter the delimiting character; for example, m{/} may be used to enhance the legibility of patterns such as /\//. See '[http://perldoc.perl.org/perlre.html perldoc perlre]' for more details.

== See also ==