sort hash in perl

Is this some type of school assignment? Why can't you use perls sort() function?

http://en.wikipedia.org/wiki/Merge_sort
http://www.devhood.com/Tutorials/tutorial_details.aspx?tutorial_id=322

Can we earn points just from posting links to articles? Seems like anyone could post links.

I'm preparing a sets of questions and answers for my interview, not school work.
And, I really need a workable version of functions, not links, Thanks.

then maybe you want to start looking at the relational and equality operators, stuff like:

>
<
>=
<=
gt
lt
ge
le
eq
ne
cmp
<=>

Why can you not use sort?  Are you saying that you can't do anything like:

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

    my %aList = ('car'=>300,'train'=>150,'truck'=>100,'bike'=>330);
   
    print "Sorted by key, alphabetically:\n\n";
    foreach my $key (sort keys(%aList)) {
       print "\t$key = $aList{$key}\n";
    }
   
    print "\nSorted by key, reverse alphabetically:\n\n";
    foreach my $key (reverse (sort keys(%aList))) {
       print "\t$key = $aList{$key}\n";
    }
   
    print "\nSorted by value, lowest to highest:\n\n";
    foreach my $key (sort value_L2H (keys(%aList))) {
       print "\t$key = $aList{$key}\n";
    }
   
    print "\nSorted by value, highest to lowest:\n\n";
    foreach my $key (sort value_H2L (keys(%aList))) {
       print "\t$key = $aList{$key}\n";
    }

sub value_L2H {
   $aList{$a} <=> $aList{$b};
}

sub value_H2L {
   $aList{$b} <=> $aList{$a};
}

this is the question that made up by the supervisor, and our job is to turn in
the answer, and myself is not a decent perl programmer. What I mean for
the problem to solve is:

is it possible to print out a hash contents in ASCII order with respect to the
key(car, bike, truck) and the value(330, 300, 150), without using the "sort" function?
The result will be the same like mjcoyne has provided, but without using "sort".

So is it a question of using some clever thing, like the fancier hash Ozo has pointed to (with the SortByKey and SortByValue re-ordering methods -- what do you want to bet that they're implemented using 'sort'?) or of implementing your own sort function in Perl?