imap split-fancy greedy match?

[Emanuel Evans]

Hi! I'm trying to use fancy splitting with nnimap like so:

--8<---------------cut here---------------start------------->8---
(nnimap-split-fancy
 (| (to "\\([-_[:alnum:]]+\\)@noreply\\.github\\.com" "github.\\1")
    ;; etc.
    ))
--8<---------------cut here---------------end--------------->8---

The problem: it seems to not match the whole "To" field, so (for
instance) "database_cleaner@noreply.github.com" gets filed into the
"github.cleaner" group instead of "github.database_cleaner". Weirdly, I
can workaround by having a more explicit regexp such as
"\\(\\w+[-_]\\w+\\)@noreply\\.github\\.com", but I don't want to do that
for every combination of groups and punctuation. (This doesn't seem to
be a problem with non-fancy splitting.) Is there any way to make sure
that fancy splitting matches the whole field "greedily"?