Wrapping consecutive similar elements inside a new parent element

I'm cleaning up HTML exported from Word documents.  First, I run Tidy again
the exported HTML, to convert it to well-formed XHTML, then I transform it
with my own XSLT stylesheet.

I need to convert (this is slightly simplified):


<p>Some paragraph that does not begin with a span element whose first
character is a hyphen.</p>
<p><span>-</span>List item</p>
<p><span>-</span>List item</p>
<p><span>-</span>List item</p>
<p><span>-</span>List item</p>
<p>Some paragraph that does not begin with a span element whose first
character is a hyphen.</p>
<p><span>-</span>List item</p>
<p><span>-</span>List item</p>
<p><span>-</span>List item</p>
<p><span>-</span>List item</p>
<p>Some paragraph that does not begin with a span element whose first
character is a hyphen.</p>


into this:


<p>Some paragraph that does not begin with a span element whose first
character is a hyphen.</p>
<ul>
<li>List item</li>
<li>List item</li>
<li>List item</li>
<li>List item</li>
</ul>
<p>Some paragraph that does not begin with a span element whose first
character is a hyphen.</p>
<ul>
<li>List item</li>
<li>List item</li>
<li>List item</li>
<li>List item</li>
</ul>
<p>Some paragraph that does not begin with a span element whose first
character is a hyphen.</p>


I'm afraid my attempts at this have been truly pitiful:


        <xsl:template match="p[starts-with(span[1], '-')]">

                <xsl:if
test="not(starts-with(preceding-sibling::p[1]/span[1], '-'))">
                        <xsl:text>&lt;ul&gt;</xsl:text>
                </xsl:if>

                <li>
                        <xsl:apply-templates />
                </li>

                <xsl:if
test="not(starts-with(following-sibling::p[1]/span[1], '-'))">
                        <xsl:text>&lt;/ul&gt;</xsl:text>
                </xsl:if>
        </xsl:template>


I know, I know: those <xsl:text>&lt;ul&gt;</xsl:text> bits are a joke, they
don't produce the <ul> parent element.

I've tried writing a template that uses <xsl:for-each>, but that ends up
grabbing all following-sibling <p> elements that begin with <span>-</span>.
I don't know how to stop the <xsl:for-each> at the first non-matching <p>
element.

Can anyone throw me an XSLT pearl?

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list