Selectively applying Identity transform to multiple i

Dear colleagues,

I have a newbie question.

In my XSLT, in addition to my main input, I am reading a second input in
my XSLT using the document() function.
The second input's URL is specified via an <xsl:param>:

    <xsl:param name="input2" select="''"></xsl:param>

I need to produce output tree that is either the identity transform of
the main input or the second input depending upon whether the parameter
$input2 is null/empty or not. If it is null/empty then the main input
should be copied to output tree. If it is not null/empty then the second
input should be copied to output tree.

I have been unable to do this correctly after much trying.

Can someone provide some guidance on how to accomplish this seemingly
simple task?

Thanks for your help.

-- 
Regards,
Farrukh

Web: http://www.wellfleetsoftware.com