Check bgp_path.len without some AS

Hi, For some route selection configurations I need to check the bgp_path.len without some AS numbers. I tried something like: bgp_path.delete(AS_1); bgp_path.delete(AS_2); if bgp_path.len < N then ... But doing this I modify permanently the AS path. I've tried using a temp variable, but looks like bird doesn't allow to create bgppath "variables". Any ideas about how this could be achieved? Thanks! Xavier