MSIE: testing attribute values

Has anyone successfully used <xsl:if> in MSIE 5b2 to test whether an
attribute has a specific value?  The MS documentation states that the
match attribute takes "a subset of the XSL Pattern Match Syntax", but
does not give details.  Here's what I've found:

<xsl:if match=".">                  works.

<xsl:if match="./child">            doesn't work.

<xsl:if match="*[0]">               works.

<xsl:if test="@attribute">          doesn't work.  (I don't know where
                                    "test" came from; it's one of the
                                    two examples provided in the MS
                                    doc.)

<xsl:if match="ancestor(elmtype)">  works.

<xsl:if match="ancestor(elmtype/child)">
                                    is true whether or not child is
                                    there, and even if child is not an
                                    ancestor of the current node
                                    (counter to the doc).

<xsl:if match="ancestor(elmtype[child])">
                                    is true whether or not child
                                    exists.

<xsl:if match="ancestor(elmtype[@attribute]")>
                                    is always true, which is strictly
                                    correct since attribute has a
                                    default value specified in the
                                    DTD.

<xsl:if match="ancestor(elmtype[@attribute='false'])">
                                    is always true, even for elements
                                    on which attribute is explicitly
                                    specified as "true".

<xsl:if match="ancestor(elmtype)/@attribute">
                                    is always false, even for elements
                                    on which attribute has an explicit
                                    value.

Can anyone help me puzzle this out?

-Chris
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