use Sort::Versions

#!/usr/local/bin/perl -w
use strict;
use Sort::Versions;

my @old = ("99B","99","99A","100A","100","101","88");

print "$_\n" for sort { versioncmp($a,$b) } @old;
[download]

output:

88
99
99A
99B
100
100A
101
[download]