Source build based on recipe fails with the error 'sh: Bad substitution'

Hello,

I'm currently preparing some 'recipes' for the Cairo-Dock project.
It works great for the 'Core' part for Lucid series: https://code.edge.launchpad.net/~matttbe/+recipe/cairo-dock-test-build-lucid
But not for its plug-ins: https://code.edge.launchpad.net/~matttbe/+recipe/cairo-dock-plug-ins-test-build-lucid
I've this error only if I launch the 'recipe' on LaunchPad for Lucid series: "sh: Bad substitution" (the full buildlog.txt is available there: http://launchpadlibrarian.net/51790437/buildlog.txt.gz). It's a bit strange because I don't have any error if I try this 'recipe' locally (on Ubuntu Maverick 64bits) with this command:
    $ bzr dailydeb cairo-dock-plug-ins.recipe test/
and this is the content of cairo-dock-plug-ins.recipe:
    # bzr-builder format 0.2 deb-version 2.2.0-0beta2-{revno:core}-0ubuntu1~ppa0~lucid
    lp:cairo-dock-plug-ins
    nest packaging lp:~cairo-dock-team/cairo-dock-plug-ins/debian-dailydeb-lucid-plug-ins debian
    nest core lp:cairo-dock-core tmp
Can I use two 'nest' commands for Lucid series?

Thank you for this great tool!

PS: Cairo-Dock Core is an API and Cairo-Dock Plug-ins uses this API. So the latest revision of the Plug-ins branch has to be compiled with the latest version of the Core branch. This is why I've to add this line in the recipe file:
     nest core lp:cairo-dock-core tmp
only to use "{revno:core}" and having the same deb-version for the both packages.