A user reported a problem whereby a script
would fail, claiming the shell interpreter could not be found. In fact
revealed a mangled path like
with various unexpanded variables. The node in question had the custom environment variable property set, where in particular PATH was set to an expression involving $PATH as well as various other sister properties.
Freestyle projects were building without problem on this node, so it seems that the Workflow node step was failing to expand variable references picked up from the custom property.