Good point on the $^T bit, I missed that. I'd actually think it was more of a problem with a short-lived task though such as a CGI. For example, if a CGI took a maximum of ten seconds to run then there'd only be ten possible values, increasing the possibility of a clash?

On another note you may hit $$ problems if the same process wants multiple IDs, but by this point you'd be wise to look at something like class::singleton to guarantee a single-point ID manager.