How to sort numbers in Perl

You can pass a custom comparison function to Perl's sort routine. Just use:

@sorted = sort { $a <=> $b } @unsorted;

The sort function accepts a custom comparison function as its first argument, in the form of a code block. The {...} part is just this code block (see http://perldoc.perl.org/functions/sort.html ).

sort will call this custom comparison function whenever it needs to compare two elements from the array to be sorted. sort always passes in the two values to compare as $a, $b, and the comparison function has to return the result of the comparison. In this case it just uses the operator for numeric comparison (see http://perldoc.perl.org/perlop.html#Equality-Operators ), which was probably created just for this purpose :-).

Solution shamelessly stolen from "Perl Cookbook", Chapter 04 Sub-chapter 15 (buy the book - it's worth it!)

Perl's sort by default sorts alphabetically in ASCII order. To sort numerically you can use:

@sorted = sort { $a <=> $b } @_;

Supply a comparison function to sort():

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

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

The default sort function is cmp, string comparison, which would sort (1, 2, 10) into (1, 10, 2) . <=> , used above, is the numerical comparison operator.