while (my ($key, $value) = each %my_hash) {
   .
   . # some processing on the element
   .
}

##</code><code>##

for my $key (keys %my_hash) {
   my $value = $my_hash{$key}    # and no need to change the code below
   .
   . # some processing on the element
   .
}

##</code><code>##

for my $key (my @temp = keys %my_hash) {
   my $value = $my_hash{$key}    # and no need to change the code below
   .
   . # some processing on the element
   .
}