I would guess a custom sort black ... like the following test :

@a = qw(39 45 120 139);
@b = sort(@a);

@c = sort { $a <=> $b } @a;

print "B : ",join(',',@b),"\n"; # B : 120,139,39,45
print "C : ",join(',',@c),"\n"; # C : 39,45,120,139
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"They shall not overcome. Whoever told them that the truth shall set them free was obviously and grossly unfamiliar with federal law."
    -- John Ashcroft