Import pegasus mail folders to cyrus
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It's not very elegant (particularly in that parts of it use different IMAP perl modules (don't ask) ), and it only recreates your hierarchy one level deep. I found it worked pretty nicely, though. You should note that I assume you are using unix hierarchy seperators in Cyrus. You will also need to download peg_split_and_deliver.pl, and peg_folder_hierarchy.pl for it to work, along with some CPAN modules.
All code is free software under the GNU GPL.