#define sv_catpvn_nomg_maybeutf8(dsv, sstr, slen, is_utf8) \
sv_catpvn_flags(dsv, sstr, slen, (is_utf8)?SV_CATUTF8:SV_CATBYTES)
#define sv_catpvn_nomg_maybeutf8(dsv, sstr, slen, is_utf8) \
sv_catpvn_flags(dsv, sstr, slen, (is_utf8)?SV_CATUTF8:SV_CATBYTES)