#!/usr/bin/perl

use strict;

# this is the hash I want to keep results in
my %count = ();
# there are way more lines than this but anyway...
for my $i (1 .. 100){
# this just represents that I've found a pair and want to run the sub
 if ($i % 50 == 0){
# run the sub
  &inc(\%count);
  }
 }

# I need access to the hash that's updated in the sub
print $count{'count'}."\n";

sub inc {
 my $c = shift;
 # make a change to the hash
 $c->{'count'}++;
 # pausing for affect!
 # this simulates that the sub takes a while to run
 sleep(10);
 }