#!/usr/bin/perl -w
    use strict;

    my $sortname = shift;
    print join ' ', sort $sortname 1..20;

    sub num { $a <=> $b }
    sub alpha { $a cmp $b }

##</code><code>##

    % foo.pl num
    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

    % foo.pl alpha
    1 10 11 12 13 14 15 16 17 18 19 2 20 3 4 5 6 7 8 9

##</code><code>##

    SUBNAME may be a scalar variable name
    (unsubscripted), in which case the value provides
    the name of (or a reference to) the actual subroutine
    to use.  In place of a SUBNAME, you can provide a
    BLOCK as an anonymous, in-line sort
    subroutine.