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Re^3: Making a regex case insensitive

by johngg (Abbot)
on Mar 06, 2007 at 21:17 UTC ( #603515=note: print w/ replies, xml ) Need Help??


in reply to Re^2: Making a regex case insensitive
in thread Making a regex case insensitive

While the case of '--' and ';' seems to be a matter of debate and jocose comment, you might like to know that you can switch case sensitivity on and off in different parts of a regular expression. You would use constructs like (?i), (?-i), (?i:text) and (?-i:text). The first two switch case insensitivity on and off respectively. The second two just apply their effect, insensitive or sensitive respectively, to the text inside the parentheses. Here is a contrived example that uses a precompiled (qr{ ...}) regular expression that also uses extended syntax, the x, to allow comments and white space inside the expression.

use strict; use warnings; my @strings = ( q{catFiSHcake}, q{DogFISHcAkE}, q{cATfishCake}, q{caTFISHcaKE}); my $rxMixed = qr {(?xi) # use extended syntax and # make case insensitive (?:cat|dog) # non-capture alternation # of cat or dog (?-i:FISH) # FISH, case sensitive # inside parentheses cake # cake, case insensitive # again }; foreach my $string ( @strings ) { print qq{$string: }, $string =~ $rxMixed ? qq{Match\n} : qq{No match\n}; }

Here's the output.

catFiSHcake: No match DogFISHcAkE: Match cATfishCake: No match caTFISHcaKE: Match

I hope this is of interest.

Cheers,

JohnGG


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