Hmmm POSIX..... does that come installed with Perl? If not, how can I tell if it is already installed? If not installed where can I grab it from, etc..,? Right now when I try including use POSIX qw/tan/; the Perl cgi app I have comes back with a cgi error page.
There is of course also Math::Trig (in fact the POSIX entry for tan() also references this).
It also is part of Perl's core distribution, but if your administrator has been doing things to the distribution (which might account for your error), then all bets are off.