I couldn't help it...it looked like too much fun trying to crunch this code to its smallest form:P

use strict;
my @foo = ("23 hours","22 minutes","21 seconds","20 miliseconds","0 na
+noseconds");
my $final;
$final?($final =pop(@foo).", $final"):($final =($#foo>1)?"and ".pop(@f
+oo):pop(@foo)) until not @foo;
print "$final\n";
[download]

update: I removed an extra space in the output string and a wee mistake (it functioned correctly but it was useless code) from a previous attempt