[Zope] How to insert variable from expression?

[Jaroslav Lukesh]

Hi all,

I have file#(DTML Document), that have image with same name, but with
extension for image
type. 

file1
file1.gif
file2
file3
file3.gif

So what Can I do insert image with that composite filename? And if
missing, insert nothing.

<dtml-in.....(DTML Document)...>
	.......
	<dtml-var expr="_['id'] + '.gif'" missing> ???
</dtml-in>

It insert filename.gif only,no picture. render(_['id'] + '.gif') does not
work, wrong syntax?

I was read "Basic COncepts" (aka book3) chapter 4.2.1 (Computed Object
access), example 3.5 and _[prefix + 'suffix'] does not work :(

Many thanks

             Jaroslav Lukesh