nim.pl

#!/usr/bin/perl
use warnings;
use strict;
my $board = 12;
sub board($) {
  print "There are $board board pieces left.\n";
  print "\n".$_[0]." Wins!\n\n" if($board <= 0);
}
sub take($$) {
  my ($p,$t) = @_;
  return 0 if(($t > 3) || ($t <= 0) || ($t > $board)) && (print "Invalid input!\n");
  print "$p takes $t pieces\n"; $board -= $t; board($p); 1;
}
sub getInput($) { print($_[0].': '); chomp(my $result = <STDIN>); int($result); }
START: {
  $board = getInput('Starting pieces') or redo;
  redo if($board < 4) && (print "Too few pieces!\n");
}
while($board > 0) {
  PLAYER: { take('Player', (getInput('How many pieces do you want to take (1-3)') or redo)) or redo; }
  take('NIM',$board % 4 || 1)
}