That's because sort does a lexical sort by default, and you want a numerical sort. Compare the "magic" sort variables $a and $b using the spaceship operator.
perldoc -f sort Reveals the following:

# sort numerically ascending
@articles = sort {$a <=> $b} @files;

# sort numerically descending
@articles = sort {$b <=> $a} @files;
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Cheers
Update:Ahah!. Knew it was around here somewhere! Under Categorized Questions and Answers, in the sorting subsection (Although it might benefit from being in the array section as well), you'll find How do I sort a list of numbers?

davis
Is this going out live?
No, Homer, very few cartoons are broadcast live - it's a terrible strain on the animator's wrist