The substr solution will work regardless of circumstances. . .

What about with CCI001 and CDI001? I think RMGir is right: the sort order is underspecified. Even something like:

# Simplified for illustration. Will not work for OP. Would benefit fro
+m ST. 
sort {
    my ($a1,$a2) = $a =~ /([A-Z]*)(\d*)/;
    my ($b1,$b2) = $b =~ /([A-Z]*)(\d*)/; 
    $a1 cmp $b1 || $a2 <=> $b2
} @list;
[download]

is likely to break with CC100A and CC100B. Given the elements that he gave us I'd think that a variation on the above would work but that guess isn't any better than yours or anyone's.

-sauoq
"My two cents aren't worth a dime.";