I'm replying here to you, moritz, not because I'm disagreeing with you but because I want to add to your advice and I think it flows better here than as another response to the OP.

Anon could fix the specific regex issue using anchors, of course. There are other issues, though, like why a regex is used in the first place when $key eq $i would have worked just as well, or why one would loop over the keys of a hash and an array containing the important keys of the hash as well in the first place.

I think your advice to be more specific about input and output is apt. I think, too, though, that the OP could use some time with each, perlre, keys, and maybe perldata, map, perlrequick, perlretut, and perlcheat.