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A Brief Note on Purity warnings

Some modules, as well as depending on other perl modules, also have non-perl components. To build these modules you normally need a working compiler.

I detect these modules by looking both at their dependencies and their MANIFEST file (which should contain a list of all files in a distribution, such as here). If a distribution depends on any of the Inline modules, or if it contains any files with any of the following extensions, then it is assumed to not be "pure perl".

• swg
• xs
• c
• h
• i

However if the string "PurePerl" appears anywhere in the MANIFEST, then I assume that there is a "pure perl" version *as well as* any "impure" version of the code, bundled up in the same distribution.

This is, of course, only a heuristic. You can't accurately determine a file's content from its filename. Possible errors from this heuristic include:

• the "pure" version has some other name - eg, Params::ValidatePP (but looking for the PP suffix will just lead to other errors, with modules like PDL::PP or Inline::CPP)
• a .c file might, for example, be used to test a module. An example of this is Text::CPP (where PP stands for pre-processor, not pure-perl; although in this case, the module isn't "pure" anyway)
• A perl file might contain C (or some other language) source in a string, and build and run it in some crazy non-XS, non-Inline way