perl -e '
use strict;
use warnings;
print "\nInitial size:\n" . qx {ps -o rss $$};

{ 
  my %x = ();
  for (my $i = 0; $i < 100000; $i++) { 
    $x{$i} = 1;
  }
  print "\nafter allocating a huge hash:\n" . qx {ps -o rss $$}; 
  for my $k (keys %x) { 
    delete $x{$k} 
  } 
  undef %x; 
  print "\nafter deallocating the huge hash\n" . qx {ps -o rss $$}; 
} 

print "\nafter the huge hash goes out of scope\n" . qx {ps -o rss $$};'