Re: Type of a variable containing values of mixed type

How can I enforce that a variable contains a particular bunch of mixed
types? Say:

     <xsl:variable name="MY_VAR" as="b&">
         <xsl:value-of select="42"/>
         <xsl:value-of select="13"/>
         <xsl:value-of select="hello"/>
     </xsl:variable>

Is there a way to enforce, with the attribute `as`, that the variable
contains a series of integers and a string (or, even, particularly 2
integers and 1 string) or else have the transformation fail?