Screw all that ... keep it simple. Presumably you are generating a web-page. So, iterate through the first list, and, for each element in the second, use the grep function to look for matching entries to $_. Use a scalar-context since the only thing you care about is whether matching-entries exist. If the result is greater-than-zero, generate the "Match!" string in the second column. Data-volumes in the "thousands of" records frankly do not warrant the use of more-advanced magick.