Given the simple nature of the data, i.e. each element startswith 'ch', I'm surprised others didn't do this:

my @sorted = sort { substr($a,2) <=> substr($b,2) } @array;
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OK, so it's calling substr rather a lot of times, so with a large array that might be slow. Alternatively we could cache it:

@array = map {substr($_,2)} @array;
my @sorted = sort { $a <=> $b } @array;
@sorted = map { "ch$_" } @sorted;
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