sub pascal_tri_row {
    my $r = shift;
    return () if $r < 0;

    my @row = (1) x ($r + 1);

    for my $i (1 .. $r - 1)
    {
        $row[$_] += $row[$_ - 1]
          for reverse 1 .. $i;
    }
    return @row;
}

sub triangle {
    my $numTosses = shift;

    my @triangle = (0, 1, 0);
    for (1 .. $numTosses) {
        my @newTriangle=(0);
        push @newTriangle, $triangle[$_]+$triangle[$_+1] for 0 .. $#triangle-1;
        push @newTriangle, 0;
        @triangle = @newTriangle;
    }

    return @triangle;
}

use Benchmark qw(cmpthese);

cmpthese -1, {
    robo_tri => sub { triangle(32) },
    repel_tri => sub { 0, pascal_tri_row(32), 0 }, # 0's to match triangle()'s return
};

__END__

            Rate  robo_tri repel_tri
robo_tri  1128/s        --      -38%
repel_tri 1811/s       60%        --