ZlR:

I sometimes use this trick: Rather than reference the top hash everywhere, I create a reference to the "current" hash in each level of the loop, like so:

#!/usr/bin/perl -w
use strict;
use warnings;

my %rez = (
    'host1' => {
        'tgt' => {
            'target_0011' => {
                '11C3' => '0C5C',
                '11E3' => '0C7C'
            },
        },
        'wwn' => [ 'foobar' ]
    },
);

for my $curHost (keys %rez) {
    my $host = $rez{$curHost}; # Use $$host{key} at this level

    print "HOST: $curHost\n";

    for my $curDev (keys %{$$host{tgt}}) {
        my $dev = $$host{tgt}{$curDev}; # Use $$dev{key} at this level

        # without using trick:
        my $bar = $rez{$curHost}{tgt}{$curDev}{'11E3'};

        # with trick:
        my $foo = $$dev{'11C3'};

        print "    DEV $curDev contains: ", join(", ", sort keys %$dev
+), "\n";
    }
}
[download]

This way, your references aren't a foot and a half long. You can easily add or remove a level of your structure pretty easily, too, since you needn't edit a bazillion lines of code--only the ones where you change levels. I normally use this trick when (a) I suspect that I'll have to rearrange the structure or (b) my references get too long.

...roboticus