#!/usr/bin/perl

use strict;
use warnings;

my $file = "file.txt";

CreateFile($file);

system frobnicate => $file;

sub CreateFile {
  my $f = shift;
  open(OUTPUT_FILE, ">$f") or die "Err: $!";
  for (1..100) {
    print OUTPUT_FILE "$_\n";
  }
  # blah, blah, blah...
  close OUTPUT_FH
}