maybe this diff is helpful.

there is a change in the xs file:

-SV*
-_xml2hash(xml,conf)
-               char *xml;
+void
+_xml2hash(xml_sv,conf)
+               SV *xml_sv;
                HV *conf;
        PROTOTYPE: $$
-       CODE:
+       PPCODE:
+               SvGETMAGIC(xml_sv);
+               char *xml = SvPVbyte_nolen(xml_sv);
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after all without adding the utf8decode option xml2hash marks your hash value as utf8.