No way we can help until you provide some code we can run. Start with the following template and add data to reproduce your failure:

use strict;
use warnings;

my $userinput = 'Blah';

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

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

Matched user input against Blah <- that should match
[download]