If I may add, be careful of this construct:

foreach $keys (%msgids) {
            if ($key =~ /$line/) {
                delete $msgids $key;
            }
      }
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You probably meant:

foreach $key (keys %msgids) {
            if ($key =~ /$line/) {
                delete $msgids{$key}
            }
      }
[download]

This will probably create a large temporary list in memory (keys %msgids) (and you seem to be missing a close brace).
A better way to iterate through a hash is to use each:

while (($key, $value) = each(%msgids)) {
            if ($key =~ /$line/) {
                delete $msgids{$key}
            }
      }
[download]