I prefer davidrw's map method, for this comparision, but in case anyone stumbles upon this and wants an alternative - you can use a hash instead:

my ($points, $quota) = @_;
my %compare = (
   18000 => 24,
   16000 => 23,
   14000 => 22,
    ... );
for my $key (sort {$b <=> $a} keys %compare)
{
  if ($points > $key and $quota < $compare{$key})
  {
    return $compare{key};
  }
}
return 15;
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Check out QM's reply for a better example

Update: it doesn't work for 16626 => 21, because it assumes the keys increment in conjuction with the values, which 16626 => 21 breaks. Added link.