Re: unpacking percent-escaped URI components

Unpacking RFC 4122 percent-escaped strings for code points less than
256 is straightforward --

tokenize($value,'%')[normalize-space()] ! local:H2D(.) !

where local:H2D is a hex-digits-to-decimal-integer function.

When the escaped value goes above 255, as with U+201C and U+201D, bb,
the escapes start being multi-octet UTF-8, so %E2%80%9C and %E2%80%9D.

Is there a useful way to turn those multi-octet escapes back into single
characters in XPath or XSLT?

(tokenize($value,'%')[normalize-space()] ! local:H2D(.)) =>
saxon:octets-to-hexBinary() => saxon:hexBinary-to-string('UTF8')