C<AvARRAY> points to the first element in the array that is visible from
Perl, C<AvALLOC> points to the real start of the C array. These are
usually the same, but a C<shift> operation can be carried out by
-increasing C<AvARRAY> by one and decreasing C<AvFILL> and C<AvLEN>.
+increasing C<AvARRAY> by one and decreasing C<AvFILL> and C<AvMAX>.
Again, the location of the real start of the C array only comes into
play when freeing the array. See C<av_shift> in F<av.c>.
slightly differently. A flag in the SV, C<SVf_UTF8>, indicates that the
string is internally encoded as UTF-8. Without it, the byte value is the
codepoint number and vice versa (in other words, the string is encoded
-as iso-8859-1). You can check and manipulate this flag with the
+as iso-8859-1, but C<use feature 'unicode_strings'> is needed to get iso-8859-1
+semantics). You can check and manipulate this flag with the
following macros:
SvUTF8(sv)