saintex, But in your code you are not using the reference at all. I think if you want to change the original values, Then pass by reference and change it.

#!/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
    .......
}
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