i don't have a reply to your question directly, but wouldn't only one split work better?

my %hash = map {
     my ( $one, $two ) = (split /:/, $_ )[0,2];
     $one => $two;
    } <FILE>;
[download]

i didn't test this... so i can't be sure. it just seems more efficient to only split once. you can also test the values of $one and $two to see if you can find the problem.

Update: yep, i guess he did say he won't actually be using two splits. my bad... i take it all back!