env-fold for Guile?

[Carl Sorensen]

I'm trying to look through all the bindings in a top-level environment and
pull out any that include "-tuning" in their name.

It appears to me that the bindings are stored in a hash table, and I ought
to be able to do a fold procedure on a hash-table to check out all the
bindings.  But I can't find any way to access the hash table, or any
procedure that will fold the environment hash table for me.

Is this possible to do in guile?

Thanks,

Carl