Yes you can, thats what META files are for, you simply tell writemakefile the depends, when you make dist METAL files are generated, then when user try to install cpan/cpanp/cpanm notice from metal files what the "BUILD_REQUIRES" ...

Not sure if this would work, specially because the distribution already generates the mentioned files (see here). Check out this test result too. I made a stupid mistake when trying to avoid calling Inline at each call, I just need to execute it once and write the constant elsewhere. But doing that inside the Makefile.PL is not an option... I could have used require inside a eval block to trap the exception, but then the module wouldn't be created anyway. The cpan client will search and install dependencies right after the Makefile.PL is executed, but then it is too late to use it for the code generation.

A ".PL" file (as described by ExtUtils::MakeMaker) would be the best option, if I could control when it will be executed...