Recursion is another solution to this, especially if you do not know upfront how deep your hashes are nested or if the depth is not the same everywhere: 

use strict;
use warnings;

sub loop_over_hash {
    my( $keys, $href ) = @_;
    print join( ',', @$keys , $href ), "\n" and return unless 'HASH' e
+q ref $href;
    loop_over_hash( [ @$keys, $_ ], $href->{$_} ) for keys %$href;
}

my %hash = (
            a => {
                  1 => { x => 5, y => 6 },
                  2 => { s => 7, t => 8 }
                  },
            b => {
                  3 => 'end',
                 },
);

loop_over_hash [], \%hash;

[download]

In reply to Re: Hash with three keys by hdb
in thread Hash with three keys by Jeri

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.