use strict;
use warnings;

while(<DATA>) {
  s/\@MAC\((\w+),(\w+),(\w+),(\d+)\)/mac($1, $2, $3, $4)/ge;
  print;
}
sub mac {
  my ($res, $x, $y, $n) = @_;
  $n--;
  my @mac = map { "($x$_*$y$_)" } 0..$n;
  while (@mac > 2) {
    @mac = map {
      "($mac[$_]+$mac[$_+1])"
    } grep {
      !($_ % 2)
    } 0..$#mac;
  }
  "$res = " . join("+", @mac);
}

__DATA__
@MAC(Output,X,Y,2);
@MAC(Result,X,Y,8);