Question

1) %hash = (
    1 => 'a',
    4 => 'g',
    7 => 'h'

);

WAP to reverse of the given hash without using reverse function?

Answer 1

You should really learn Perl – it is really fun when you learn it yourself.

It is really that simple:

my %rev;
foreach my $key (keys %hash) {
    $rev{$hash{$key}} = $key;
}