#!/usr/bin/perl
use strict;
use warnings;

{
  # These 3 sub routines share this variable
  # but the variable can not be accessed outside this block

  my $counter = 100;

  sub increment
  {
    $counter++;
  }

  sub decrement
  {
    $counter--
  }

  sub view
  {
    print "counter: $counter\n";
  }
}

view();
increment();
view();
increment();
view();
increment();
view();
increment();
view();
increment();
view();
decrement();
view();
decrement();
view();
decrement();
view();