chomp($input = <STDIN>);
...
    chomp($output = <STDIN>);
...
open (INPUT, "$input") || die "died opening input\n";#opening up ngc18
+8cata and putting it into INPUT#

open (STDOUT, ">$output") || die "died opening output\n"; #opening up 
+ngc188cat2 and setting output of out#
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Do not use user-input filenames this way unless you place full trust in your user (and even then, it's a lousy habit to develop); this form of open can be used to run arbitrary processes (e.g. $input = "rm -rf /some/critical/directory |"). Use three arg open instead, or explicitly specify the mode and a space, e.g.:

  open(INPUT, "<", $input) or die ...
  open(OUTPUT, ">", $output) or die ...
or
  open(INPUT, "< $input") or die ...
  open(OUTPUT, "> $output") or die ...
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