It seems you already have an answer. However I have a little suggestion to improve your series of OR'd expressions. Instead of writing

($line =~ m/ex21/igm || $line =~ m/EX\-21/igm || 
 $line =~ m/exhibit\-21/igm || $line =~ m/exhibit21/igm)
[download]

instead try this:

$line =~ /ex(?:hibit)?-?21/i
[download]

This matches an 'ex' optionally followed by 'hibit' optionally followed by '-' and then ending in '21'. You don't need the /g modifier if you are only looking for one match and you don't need the /m modifier if you aren't matching with ^ or $. This is shorter and to my eyes easier to read and therefore maintain. HTH.