Er, in the perl API all the public functions are defined as Perl_<whatever> and documented without the Perl_ prefix, they are also available without the prefix through macros defined in embed.h. This was the case equally for the 5.6 MacPerl source that you originally looked at. I pointed you at the APC repository not because there was any particular difference in that function (except for some tidying and type changes they are largely identical between the two versions,) but simply because the MacPerl source you pointed to is more than four years old and based on the 5.6 source, whereas the APC reflects the current versions of Perl.

/J\