use strict;
use warnings;


my %var = (
            'a' => {
                    'one' => '1',
                    'two' => '2',
                    'three' => '3',
                },
            'b' => {
                    'four' => '4',
                    'five' => '5',

                }
        );


foreach (keys %var ) {      ## Here $_ will have a , b
        foreach (keys %{$var{$_}} ) {  ## Here $_ will have one, two , three, etc.
                print $_;               ## With in this for loop, I want to access a and b.
                }
}