What does # mean in plpgsql?

What does the hash mark (#) mean in plpgsql?

I saw it used in the pseudo_encrypt function @
http://wiki.postgresql.org/wiki/Pseudo_encrypt, on the line:

r2 := l1 # ((((1366.0 * r1 + 150889) % 714025) / 714025.0) * 32767)::int;

My google-fu has failed me on this one, and I needs to know.

Thanks!


-- Stephen