my @sorted =
   map  { $_->[0] }
   sort { $a->[1] cmp $b->[1] } # or <=>, or $b before $a
   map  { [$_, f($_)] }
   @unsorted;

##</code><code>##

# the first map does this
qw(8 11 9 4 3) --> (
  [ 8, "viii"],
  [11, "xi"],
  [ 9, "ix"],
  [ 4, "vi"],
  [ 3, "iii"],
)

##</code><code>##

# the sort does this:
(
  [ 8, "viii"],
  [11, "xi"],
  [ 9, "ix"],
  [ 4, "vi"],
  [ 3, "iii"],
) --> (
  [ 3, "iii"],
  [ 9, "ix"],
  [ 4, "vi"],
  [ 8, "viii"],
  [11, "xi"],
)

##</code><code>##

(
  [ 3, "iii"],
  [ 9, "ix"],
  [ 4, "vi"],
  [ 8, "viii"],
  [11, "xi"],
) --> qw( 3 9 4 8 11 )

##</code><code>##

use strict;
use warnings;
use Roman ();

my @unsorted = qw(8 11 9 4 3);
*f = \&Roman::roman;

my @sorted =
   map  { $_->[0] }
   sort { $a->[1] cmp $b->[1] } # or <=>, or $b before $a
   map  { [$_, f($_)] }
   @unsorted;

print "@sorted\n";

__END__ # output shown below
3 4 9 8 11

##</code><code>##

my @sorted = sort { f($a) cmp f($b) } @unsorted;

##</code><code>##

*f = sub {
	$::count++;
	END { print "f() called $::count times\n" };
	goto \&Roman::roman;
};

##</code><code>##

use List::Util "shuffle";
my @unsorted = shuffle(1..100);