Your grep returns all the elements of @contents that are NOT matched by your regex, so that will always be true. Removing the ! from your grep should fix that, assuming the rest of the code that we can't see is okay.

This is not the best way to do this, though, because you're looping through the contents of one file for each line in the other file. The standard way to "match lines from one file to keys from another file" is to load the keys from one file (file2) into a hash as its keys, then go through the other file (file1) splitting out the matching part and seeing if it exists as a key in the hash. If it does exist, print it.

Try coding it that way, and let us know if you need help.