@ranked = sort { $a->{FIRST} cmp $b->{FIRST} or $a->{LAST} cmp $b->{LAST} or $a->{AGE} <=> $b->{AGE} } @employees;


##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use Sort::Key qw(multikeysorter);

my @employees = ( 
    { FIRST => 'Bill',   LAST => 'Gates',     
      SALARY => 600000, AGE => 45 },
    { FIRST => 'George', LAST => 'Tester',
      SALARY =>  55000, AGE => 29 },
    { FIRST => 'Sally',  LAST => 'Developer', 
      SALARY =>  55000, AGE => 29 },
    { FIRST => 'Joe',    LAST => 'Tester',    
      SALARY =>  55000, AGE => 29 },
    { FIRST => 'Steve',  LAST => 'Ballmer',   
      SALARY => 600000, AGE => 41 } 
);

my %types = (
             FIRST  => 'str',
             LAST   => 'str',
             SALARY => 'int',
             AGE    => 'int',
            );

my @sort = @ARGV; # not comma-separated, just for ease
@sort = map uc, @sort; # so I don't have to hold the shift key down.
my $sorter = multikeysorter( sub { my $A = $_; map { $A->{$_} } @sort }, @types{@sort} );
my @ranked = $sorter->(@employees);

foreach my $emp (@ranked) {
    print "$emp->{SALARY}\t$emp->{AGE}\t$emp->{FIRST}\t$emp->{LAST}\n";
}


##</code><code>##

$ perl x.pl first age
600000  45      Bill    Gates
55000   29      George  Tester
55000   29      Joe     Tester
55000   29      Sally   Developer
600000  41      Steve   Ballmer
$ perl x.pl age first
55000   29      George  Tester
55000   29      Joe     Tester
55000   29      Sally   Developer
600000  41      Steve   Ballmer
600000  45      Bill    Gates
$ perl x.pl age last first
55000   29      Sally   Developer
55000   29      George  Tester
55000   29      Joe     Tester
600000  41      Steve   Ballmer
600000  45      Bill    Gates


##</code><code>##

@types{map -$_, keys %types} = map -$_, values %types;

##</code><code>##

my $sorter = multikeysorter( sub { my $A = $_; map { $A->{s/^-//r} } @sort }, @types{@sort} );

##</code><code>##

$ perl5.14.2 x.pl -age last first
600000  45      Bill    Gates
600000  41      Steve   Ballmer
55000   29      Sally   Developer
55000   29      George  Tester
55000   29      Joe     Tester


##</code><code>##

my $sorter = multikeysorter( sub { my $A = $_; map { (my $k = $_) =~ s/^-//; $A->{$k} } @sort }, @types{@sort} );