That's because the syntax of the for loop is wrong; you probably want ; instead of , in there.

With the commas it's just a 3-element list (0, 1, 0) over which the for iterates. But you can write that even easier:

for (1..$n) {
    # body of the loop goes here
}
[download]

See perlsyn for more information about the syntax of for-loops (scroll down to subsection "Foreach Loops").