use strict;
use warnings;

my $userinput = 'Blah';

while (my $record = <DATA>) {                     
    print "Matched user input against $record" if $record =~ m/$userinput/g;
}

__DATA__
Blegh
Blah <- that should match
blah <- and that won't
Yuck

##</code><code>##

Matched user input against Blah <- that should match