conversion flags, and I<result> should be NULL or a pointer to an NV.
The scan stops at the end of the string, or the first invalid character.
Unless C<PERL_SCAN_SILENT_ILLDIGIT> is set in I<*flags>, encountering an
-invalid character will also trigger a warning.
+8 or 9 will also trigger a warning.
On return I<*len> is set to the length of the scanned string,
and I<*flags> gives output flags.