[Zope] Build-in functions

[Axel Missbach]

Trying to use the build-in python string functions like replace without
success.

I want to replace the slash with a dot in an URL
(main/detail/form/index=> main.detail.form.index),
but 

<dtml-let g="main/detail/form/index">
 <dtml-var replace(g,'/','.')>
</dtml-let>

doesn't what i expect.
It tries to call the object "replace(main/detail/form/index,'/','.')".

Do i have to import the build-in functions? How?

What's the way doing the replacement?

with regards
Axel