yet another silly atemt to solve your problem:

while (get $url) {
  my $string = (split "_")[1];
  print "${string}\n"
}
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untested but should work.

--- edit ---
ARRGGG! my fault!
replace while with foreach and it schoud work. (Maybe you have to split "get $url" by "\n" so this would be better:

forach (split "\n", (get $url)) {
[download]