Well, not really, modern operating systems do not clone the full memory image when forking but use a copy-on-write machanism, so they would share the perl binary code and most of the heap data anyway.

I think, that even if you run the same process several times, the OS will not use new memory for the additional copies becauses it mmaps the executable.

Compiling perl as a dynamic library is only useful if you are compiling it to build different executables, for instance, perl and Apache+mod_perl.