Editing Delimiter (section)

==== Regular expression syntax ====
{{see also|Regular expression examples}}

In specifying a [[regular expression]], alternate delimiters may also be used to simplify the syntax for '''match''' and '''substitution''' operations in [[Perl]].<ref name="Friedl000">{{cite book | last = Friedl | first = Jeffrey | title = Mastering Regular Expressions | publisher = Oxford University Press | location = Oxford Oxfordshire | year = 2006 | isbn = 978-0-596-52812-6 }} page 472.</ref>

For example, a simple match operation may be specified in Perl with the following syntax:

<syntaxhighlight lang="perl">
$string1 = 'Nancy said "Hello World!" to the crowd.';    # specify a target string
print $string1 =~ m/[aeiou]+/;                           # match one or more vowels
</syntaxhighlight>

The syntax is flexible enough to specify match operations with alternate delimiters, making it easy to avoid delimiter collision:

<syntaxhighlight lang="perl">
$string1 = 'Nancy said "http://Hello/World.htm" is not a valid address.'; # target string
   
print $string1 =~ m@http://@;       # match using alternate regular expression delimiter
print $string1 =~ m{http://};       # same as previous, but different delimiter
print $string1 =~ m!http://!;       # same as previous, but different delimiter.
</syntaxhighlight>