in reply to Re^3: PerlIO::Layers 0.011 fails to build in macOS 10.13.3
in thread PerlIO::Layers 0.011 fails to build in macOS 10.13.3

printf("%s\n", "" "0.1" "") didn't immediately look like valid C to me (and it's not valid perl).
But C does allow that type of concatenation - whereas I guess perl doesn't really need to.
Even in assignment one can do char *x = "hello" "0.01" "world";

Cheers,
Rob