[ZPT] Including a variable which may exist in a tag

[Graham Stratton]

I have been trying to create a input tag as follows:

<input type="text" value=variable>

where variable may or may not exist - if not then value="" or no value 
tag would both be fine.  In DTML I could write:

<input type="text" value="&dtml.missing-variable;">

In a page template I'd like to write something like:

<input type="text" val:attributes.missing="value variable">

but can't find any such device.  Is there any elegant way of doing this 
in a template?

Many thanks,

Graham