Pigeonhome Sieve: check existence of a folder?

[AvV]

Dear All,

Thanks ofr the great job so far.

I have crawled the doc & web, and did not find oh to check for the 
presence of a folder ina  a mailbox?

I know about "fileinto :create" of course, but the purpose is slightly 
different: I want to automate the move into a folder based on some rules 
but *only if* an associated folder is present (which name is based on 
the rule), otherwise I will do a form of catch-all.

Example:

- INBOX
      +- abc
      +- def

- Rule detects "aaa" in someheader field: folder "aaa" not present" -> 
continue;

- Rule detect "def" in some header field: "def exists" -> fileinto "def" 
    ; stop;

Any help appreciated.

Cheers,

A/