I have one machine that has a sun4-solaris-multi in it's @INC. This would leave me to believe that it had been compiled for use in a multi-processor machine.

That is incorrect. Perl doesn't require a different compilation for multiprocessor machines, nor does Solaris require this.

However, it does mean that the perl that's using sun4-solaris-multi is a multi-threaded perl, while the other isn't.

Abigail