So, you basically have to print out a hash sorting lines using the value instead of the key, right? Keep in mind that using a hash won't allow you to keep the original relative order of the lines, but this does not affect what we're saying about the print.

If you had to sort only based upon the keys, you'd write something like this:

for my $k (sort keys %hash) {
   print "$k $hash{$k}\n";
}
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Well, you're near. Remember that sort allows you to specify a bare block of code which is actually a sub that's called to establish the relative order of two elements $a and $b. So, you'd change the things a bit like this:

my @ordered_keys = sort { order($hash{$a}, $hash{$b}) } keys %hash;
for my $k ( @ordered_keys ) {
   print "$k $hash{$k}\n"
}

sub order {
   my ($left, $right) = @_;
   # Perform comparison between $left and $right. Return
   # -1 if $left must come *before* $right, 0 if they are
   # equivalent, +1 if $left must come *after* $right
}
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You can include the code in order() directly in sort's block, of course, and use $a and $b instead of $left and $right, but do this only if readability doesn't suffer from this inclusion.

The actual implementation of the order() subroutine is left as exercise, but you could extract the last two characters from $left and $right, and use the cmp operator :)