use strict;
use warnings;

my $text  = 'Abcd';
my $match = 'abcd';
my $regex = qr/$match/;

print "No match: '$text', '$match'\n" if $text !~ /$regex/i;
print "/i match: '$text', '$match'\n" if $text =~ /$match/i;

##</code><code>##

No match: 'Abcd', 'abcd'
/i match: 'Abcd', 'abcd'