use strict;
use warnings;

my %hash;
@hash{ 'a' .. 'z' } = ( 1 .. 26 );

print 'Total elements in %hash before deletion: ',
      scalar keys %hash,
      "\n";

delete $hash{ +each %hash } for 1 .. keys( %hash ) - 5;

print 'Total elements in %hash after deletion: ',
      scalar keys %hash,
      "\n";