#!/usr/bin/perl
  use strict;

  parse(1,0);

  sub parse {
    while (defined(my $number = shift)) {
      print "Number: $number\n";
      &parse if $number;
    }
  }

##</code><code>##

  $ perl test.pl
  Number: 1
  Number: 0

  $ perl -d:DProf test.pl
  Number: 1
  Number: 0
  Number: 0

##</code><code>##

  $ perl test.pl
  Number: 1
  Number: 0
  Number: 0

  $ perl -d:DProf test.pl
  Number: 1
  Number: 0
  Number: 0