Last modified on 1 December 2012, at 15:27

Perl Programming/Regular Expressions

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Regular expressions are tools for complex searching of text, considered one of the most powerful aspects of the Perl language. A regular expression can be as simple as just the text you want to find, or it can include wildcards, logic, and even sub-programs.

To use regular expressions in perl, use the =~ operator to bind a variable containing your text to the regular expression:

$Haystack =~ /needle/;

This returns 1 if "needle" is contained within $HayStack, or 0 otherwise.

$Haystack =~ /needle/i;    # The i means "case-insensitive"
$Haystack =~ /(needle|pin)/;  # Either/Or statements
$Haystack =~ /needle \d/;     # "needle 0" to "needle 9"


Regular expression can also be used to modify strings. You can search and replace complex patterns by using the regex format s///

 $msg = "perl is ok";
 $msg =~ s/ok/awesome/;           # search for the word "ok" and replace it with "awesome"
 ($msg is now "perl is awesome")