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

my %test;

$test{'bio'}{900}{1} = 40;
$test{'bio'}{900}{2} = 45;
$test{'bio'}{901}{1} = 38;
$test{'chem'}{1800}{1} = 27;
$test{'chem'}{1800}{3} = 47;

print_recursive(\%test);

sub print_recursive {
    my ($hash,$depth) = @_;
    return unless $hash && ref($hash) =~ /HASH/i;
    $depth ||= 0;
    foreach my $key ( keys %{ $hash } ) {
	print "\t"x$depth, $key, "\n";
	print_recursive($hash->{$key},$depth+1);
    }    
}