XPath/XSLT nested predicates: how to get the context of outer predicate?

It seems that this question was not discussed on stackoverflow before, save for Working With Nested XPath Predicates ... Refined where the solution not involving nested predicates was offered.

So I tried to write the oversimplified sample of what I'd like to get:

Input:

<root>
    <shortOfSupply>
        <food animal="doggie"/>
        <food animal="horse"/>
    </shortOfSupply>
    <animalsDictionary>
        <cage name="A" animal="kittie"/>
        <cage name="B" animal="dog"/>
        <cage name="C" animal="cow"/>
        <cage name="D" animal="zebra"/>
    </animals>
</root>

Output:

<root>
    <hungryAnimals>
        <cage name="B"/>
        <cage name="D"/>
    </hungryAnimals>
</root>

or, alternatively, if there is no intersections,

<root>
    <everythingIsFine/>
</root>

And i want to get it using a nested predicates:

<xsl:template match="cage">
    <cage>
        <xsl:attribute name="name">
            <xsl:value-of select="@name"/>
        </xsl:attribute>
    </cage>
</xsl:template>

<xsl:template match="/root/animalsDictionary">
    <xsl:choose>
        <!--                                                             in <food>     in <cage>       -->
        <xsl:when test="cage[/root/shortOfSupply/food[ext:isEqualAnimals(./@animal, ?????/@animal)]]">
            <hungryAnimals>
                <xsl:apply-templates select="cage[/root/shortOfSupply/food[ext:isEqualAnimals(@animal, ?????/@animal)]]"/>
            </hungryAnimals>
        </xsl:when>
        <xsl:otherwise>
            <everythingIsFine/>
        </xsl:otherwise>
    </xsl:choose>
</xsl:template>

So what should i write in place of that ??????

I know i could rewrite the entire stylesheet using one more template and extensive usage of variables/params, but it makes even this stylesheet significantly more complex, let alone the real stylesheet i have for real problem.

It is written in XPath reference that the dot . sign means the current context node, but it doesn't tell whether there is any possibility to get the node of context before that; and i just can't believe XPath is missing this obvious feature.