output_string() and other methods check if <xsl:output> encoding attribute is UTF-8 case-sensitively. Unfortunately it seems to be quite comon to say that the encoding is "utf-8" and mean the same thing. I'm not 100% sure if CES allows the usage of utf-8 as lowercase or not, but I think it would be a nice improvement to allow a lowercase version too.
Bug #60787 for XML-LibXSLT: Allow lowercase xsl:output encoding of utf-8
This queue is for tickets about the XML-LibXSLT CPAN distribution.
Nobody in particular
mendoza [...] pvv.ntnu.no