Maybe a look at https://metacpan.org/source/RURBAN/Filter-1.59/Call/Call.xs can be helpful? If one gets passed all those cryptic macros. One can start by clarifying where that points:

out_ptr = SvPVX(my_sv) + BUF_OFFSET(my_sv) ;

and also: ninstr(out_ptr, out_ptr + n, nl, nl + 1)) which is looking for a needle = nl = "\n0" in the big haystack=out_ptr according to perlapi

In reply to Re: Combining Import and Source-Filter to implement Syntactic Macro mechanism by bliako
in thread Combining Import and Source-Filter to implement Syntactic Macro mechanism by LanX

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