A variable, parameter, template, or function name that starts with a digit is
no QName, so a processor refuses the stylesheet, and no expression could name
it anyway: $1st is a syntax error in XPath. Start the name with a letter.
Incorrect:
<xsl:param name="1st" select="'first'"/>
Correct:
<xsl:param name="first" select="'first'"/>
The local part is judged, so my:9lives is reported as well, and so is
Q{}9lives. A digit inside the braces of Q{urn:1}lives is part of the
namespace URI, and the name is sound.