#!/usr/bin/perl -w
use strict;

my %h = qw(a b c d);
&test(\%h);
while ( my ($key, $value) = each(%h) ){
	print "Key\t $key Value\t $value\n";
   }

sub test {
    my $h = shift;
    $h->{a}= "k";
	.....
	Some Code
	.......
}