Reduce the amount of memory copying. 

Test module on additional platforms.  

Investigate whether Win32 SysV IPC emulation module(s) can be
employed to provide greater portability.

Allow -size to be specified with units (e.g. 100k) [?]

Allow -mode to use characters (e.g. rwxrwx--- ) [?]

Would passing scalar references in XS improve performance?

Add additional tests