# Any word matched

while (<$words_fh>) {
   my $re = join '|',
            map quotemeta,
            split;
    
   if ( $teststring =~ /($re)/ ) {
      print("$teststring contains $1\n");
   }
}
[download]

# Each word matched

while (<$words_fh>) {
   for my $word ( split ) {
      if ( $teststring =~ /\Q$word/ ) {
         print("$teststring contains $word\n");
      }
   }
}
[download]

That first method did the trick! Thank you very very much for your help everyone. This was my first time on PerlMonks and it was fast and easy. I think now I need to convert this array of acronyms to a hash.

Oh, I see. You are simply comparing the two strings. I am positive there is a more efficient way to do this, but for a makeshift fix you could put each word of $teststring into an array. Then, foreach element, test to see if it matches $line in the aforementioned array.