[Petal] repetitive string in attrributes - advice/tactics requested

[Josh Narins]

> On Sun 28-Aug-2005 at 21:26 +0100, Bruno Postle wrote:
> > On Sun 28-Aug-2005 at 13:38 -0400, jonathan vanasco wrote:
> > > 
> > > is there any sort of magic where i would be able to not need to  
> > > specity the entire string?
> 
> > Sure something like this should do it:
> > 
> >   <div
> >     xmlns:petal="http://purl.org/petal/1.0/"
> >     petal:define="baselink: index.cgi?a=1&amp;b=2&amp;c=3"
> >   >
> >     <a
> >       href="#"
> >       petal:attributes="href string:${baselink}${foo}"
> >     >Click here!</a>
> >   </div>
> 
> Oops typo, that should be:
> 
>   petal:define="baselink string: index.cgi?a=1&amp;b=2&amp;c=3"

Can one set things with petal:define to variables? Like

petal:define="baselink string: index.cgi?${session}"

?