In the code itself, see example below:

#!/usr/bin/perl -l

# http://perlmonks.org/?node_id=1137878

use strict;
use warnings;
$| = 1;

while(<DATA>)
  {
  my @value = split;

  tr/()//d for @value; # THE FIX

  print $value[1] - $value[0];
  }

__DATA__
(15) 20
(3) 50
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