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Re: regex for case insensitive

by marinersk (Priest)
on May 31, 2017 at 06:50 UTC ( #1191671=note: print w/replies, xml ) Need Help??


in reply to regex for case insensitive

You could have caught this yourself if you would have used strictand warnings:

#!/usr/bin/perl use strict; use warnings; my @needles = ("1-2 Steps", "5-7 Steps", "8-10 Steps", "catch"); my @haystacks = ("move 1-2 steps", "move 8-10 steps to hoist", "catch +the ball"); for my $needle (@needles) { my $found; for my $haystack (@haystacks) { if ($haystack =~ /\i\Q$needle\E\i/) { print "<br>"; print "Found [$needle] in [$haystack]\n"; print "</br>"; $found++; } } if (!$found) { print "<br>"; print "Couldn't find [$needle] anywhere!\n"; print "<br>"; } }

Results in Perl yelling at you for using \i:

S:\Steve\Dev\PerlMonks\P-2017-05-31@0243-RegEx-Case-Insensitive>perl r +egex0a.pl Unrecognized escape \i passed through in regex; marked by <-- HERE in +m/\i <-- HERE 1\-2\ Steps\i/ at regex0a.pl line 12. Unrecognized escape \i passed through in regex; marked by <-- HERE in +m/\i1\-2\ Steps\i <-- HERE / at regex0a.pl line 12. <br>Couldn't find [1-2 Steps] anywhere! Unrecognized escape \i passed through in regex; marked by <-- HERE in +m/\i <-- HERE 5\-7\ Steps\i/ at regex0a.pl line 12. Unrecognized escape \i passed through in regex; marked by <-- HERE in +m/\i5\-7\ Steps\i <-- HERE / at regex0a.pl line 12. <br><br>Couldn't find [5-7 Steps] anywhere! Unrecognized escape \i passed through in regex; marked by <-- HERE in +m/\i <-- HERE 8\-10\ Steps\i/ at regex0a.pl line 12. Unrecognized escape \i passed through in regex; marked by <-- HERE in +m/\i8\-10\ Steps\i <-- HERE / at regex0a.pl line 12. <br><br>Couldn't find [8-10 Steps] anywhere! Unrecognized escape \i passed through in regex; marked by <-- HERE in +m/\i <-- HERE catch\i/ at regex0a.pl line 12. Unrecognized escape \i passed through in regex; marked by <-- HERE in +m/\icatch\i <-- HERE / at regex0a.pl line 12. <br><br>Couldn't find [catch] anywhere! <br> S:\Steve\Dev\PerlMonks\P-2017-05-31@0243-RegEx-Case-Insensitive>


Two ways to fix this.


Two key changes:

my $needle_regex = quotemeta $needle; if ($haystack =~ /$needle_regex/i) {

New code:

my @needles = ("1-2 Steps", "5-7 Steps", "8-10 Steps", "catch"); my @haystacks = ("move 1-2 steps", "move 8-10 steps to hoist", "catch +the ball"); for my $needle (@needles) { my $found; my $needle_regex = quotemeta $needle; for my $haystack (@haystacks) { if ($haystack =~ /$needle_regex/i) { print "<br>"; print "Found [$needle] in [$haystack]\n"; print "</br>"; $found++; } } if (!$found) { print "<br>"; print "Couldn't find [$needle] anywhere!\n"; print "<br>"; } }


Or, in keeping with the approach you originally took, only one change needed:

if ($haystack =~ /\Q$needle\E/i) {

Resulting in:

my @needles = ("1-2 Steps", "5-7 Steps", "8-10 Steps", "catch"); my @haystacks = ("move 1-2 steps", "move 8-10 steps to hoist", "catch +the ball"); for my $needle (@needles) { my $found; for my $haystack (@haystacks) { if ($haystack =~ /\Q$needle\E/i) { print "<br>"; print "Found [$needle] in [$haystack]\n"; print "</br>"; $found++; } } if (!$found) { print "<br>"; print "Couldn't find [$needle] anywhere!\n"; print "<br>"; } }

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