#!/usr/bin/perl -w
use strict;

my @l = (2, 4, 19, 3, 15, 30, 1, 31, 14);

print sort {&{bysort("up")}} @l;
print $/;
print sort {&{bysort("dn")}} @l;
print $/;

sub bysort {
  my $by = shift;
  if ($by eq "up") {
    return sub { $a <=> $b };
  } elsif ($by eq "dn") {
    return sub { $b <=> $a };
  } else {
    return sub { $a cmp $b };
  }
}