MULTIPLICITY—what USE_MULTI sets—allows multiple interpreters to exist in the same process.[1]

This is required to support threads (including the fork emulation on Windows). It's also required to embed multiple instances of the Perl interpreter into a (non-Perl) program.

Feel free to build without MULTIPLICITY if you don't need those things. It heard it gives a 10% performance boost.

I don't know what PERL_IMPLICIT_SYS—what USE_IMP_SYS sets—does, so I can't help there.

  1. It does this by moving all globals into a struct, and by passing a pointer to this struct to every API function. Effectively, it makes an object (in the OOP sense of the word) of the Perl interpreter.

In reply to Re: Win32 unthreaded perl builds: To USE_MULTI or not ? by ikegami
in thread Win32 unthreaded perl builds: To USE_MULTI or not ? by syphilis

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