> <xsl:param name="upperCase" select="ABCDEFGHIJKLMNOPQRSTUVWXYZ"/>

That selects the child element <ABCDEFGHIJKLMNOPQRSTUVWXYZ> of the
current node, if there are no such elements it selects nothing.

You want

<xsl:param name="upperCase" select="'ABCDEFGHIJKLMNOPQRSTUVWXYZ'"/>
                                    ^                          ^
                                    ^                          ^
                                    ^                          ^
                                    ^                          ^
                                    ^                          ^
                                    ^                          ^


David

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