=for hackers
Found in file av.c
+=item bytes_to_utf8
+
+Converts a string C<s> of length C<len> from ASCII into UTF8 encoding.
+Returns a pointer to the newly-created string, and sets C<len> to
+reflect the new length.
+
+ U8 * bytes_to_utf8(U8 *s, STRLEN *len)
+
+=for hackers
+Found in file utf8.c
+
=item call_argv
Performs a callback to the specified Perl sub. See L<perlcall>.
=for hackers
Found in file handy.h
+=item U8 *s
+
+Returns true if first C<len> bytes of the given string form valid a UTF8
+string, false otherwise.
+
+ bool_utf8_string U8 *s(STRLEN len)
+
+=for hackers
+Found in file utf8.c
+
+=item utf8_to_bytes
+
+Converts a string C<s> of length C<len> from UTF8 into ASCII encoding.
+Unlike C<bytes_to_utf8>, this over-writes the original string.
+Returns zero on failure after converting as much as possible.
+
+ U8 * utf8_to_bytes(U8 *s, STRLEN len)
+
+=for hackers
+Found in file utf8.c
+
=item warn
This is the XSUB-writer's interface to Perl's C<warn> function. Use this