I am having a heck of a time forcing single values. For example,
someone changes their first name in peoplsoft, for some reason it adds
it as a second value in our Edirectory Tree.
I have this to fix that:

<xsl:template match="modify-attr[@attr-name='Given Name']">
<modify-attr attr-name="Given Name">
<value type="string">
<xsl:value-of select="add-

which catches this, while it works most of the time,
There are a few occasions where the peoplsoft team will blank out the
value and then reset it to the correct value generating a blank
operation. In my trace it will do a remove-all on the empty string,
causing an error.