Here's my first crack, coming in at 53. 
sub num2ord {
  my $n = shift;
#          1        2         3         4         5         6         
+7
# 12345678901234678901234567890123456789012345678901234567890123456789
+0
  $n.($n=~/1.$/?'th':qw(th st nd rd)[$n=~/([123]?)$/])
}

[download]
Update: and here's my 40-char entry: 
sub num2ord {
  my $n = shift;
#          1        2         3         4         5         6         
+7
# 12345678901234678901234567890123456789012345678901234567890123456789
+0
  $n.(qw(th st nd rd)[$n=~/(1?\d)$/]||th)
}

[download]
It's not strict-safe, and will throw a warning if warnings are turned on. And I can trim one more character off, but I'll leave that up to you to find!
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re: Golf - Ordinal Suffixes by japhy
in thread Golf - Ordinal Suffixes by sauoq

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