catch sv_2mortal(newSVpvn_utf8(...))

[tonycoz]

            sv = sv_2mortal(newSVpvn_utf8(value_at, value_max - value_at + 1, do_utf8));

to (or similar):

            sv = newSVpvn_flags(value_at, value_max - value_at + 1, SVs_TEMP|do_utf8);