use strict;
use Data::Dumper;

my $h = {
   a => 1,
   b => 2,
   c => {
      d => 3,
      e => {
         f => {
            g => 4,
            h => 5,
         },
      },
   },
};

my $match;
my $find = 'g';

find_me($h);
print "$match\n";

sub find_me {
   my ($k,$v,@rest) = %{shift()};  # merlyn code ;) 
   $match = $v      if $k eq $find;
   find_me({@rest}) if @rest;
   find_me($v)      if ref $v eq 'HASH';
}