Per kennethk's suggested reference, here's one way that's pretty straight-forward:

use strict;
use warnings;

my %hash = (
5328  => 'High',
26191 => 'Very High',
57491 => 'Low',
4915  => 'High',
1499  => 'Very High',
999   => 'Low',
4323  => 'Average',
4314  => 'High',
);
print "$_ => $hash{$_}\n" 
   foreach(sort{$hash{$a} cmp $hash{$b}} keys %hash);
[download]

Which yields the output that I think you're looking for:

4323 => Average
4314 => High
5328 => High
4915 => High
57491 => Low
999 => Low
1499 => Very High
26191 => Very High
[download]

The sort doesn't care that you have duplicate entries, it treats them as eq in the cmp and doesn't change their order within the duplicates...but it does group the duplicates and puts the group in the right place in the sort.

Good luck.