The Condition that Ate Michigan

Our main loop:

      while (<INFILE>) {
        chomp;
        last if /^SCAN_CELLS/;
        $seen_CHAIN_TEST=1  if /CHAIN_TEST/;

        if (/apply/ && $seen_CHAIN_TEST) {
          ...
        }
      }

Becomes:

      while (<INFILE>) {
        chomp;
        last if /^SCAN_CELLS/;
        $seen_CHAIN_TEST=1  if /CHAIN_TEST/;
        next unless /apply/ && $seen_CHAIN_TEST;

        ...
      }