if( $input =~ /$first/i ){ ... }

##</code><code>##

# prompt for $filename
open HINTS, "Hints.txt" or die "Can't find file\n";
while( my $hintline = <HINTS> ){
  my ($first,$last) = split(/\ == /,$hints);
  my $results = `strings $filename | grep -i '$first'`;
  next unless length $results;
  printf "Found: %s\n", $last;
}
close HINTS;