ipurge syntax

[Patrick Boutilier]

How can you get ipurge to only work on the INBOX? If I try this nothing 
happens:

ipurge -d 31 user.spam


If I put in -f then the INBOX and every folder underneath gets processed.


man page seems to indicate that only processing the INBOX is not possible:

Ipurge by default only deletes mail below shared folders, which means 
that  mails  in  mailbox(es)  below  INBOX.*  and  user.*  stay
        untouched. Use the option -f to also delete mail in mailbox(es) 
below these folders.