More Guile 1.8 code failing in 2.x

[Richard Shann]

We have one more construct being refused as we upgrade to guile 2.0 in
GNU/Denemo

(if (not (defined? 'ToggleTripleting::InsideTriplet))
    (define ToggleTripleting::InsideTriplet #t))

It is intended to set up a flag which toggles between true and false on
each call. If already set up, the flag is not altered.

Apparently (I haven't been able to check) Guile 2.0  gives an error.

#f definition in expression context, where definitions are not allowed, ((line 
. 2) (column . 4) (filename . #f)) (define ToggleTripleting::InsideTriplet #t) 
#f)

Can anyone suggest what could replace that? I would prefer to to replace
it with something that has the same semantics, rather than setting up
some alternative method of handling the situation - registering all such
variables on program startup, or some such - as at the moment this code
only evaluated if used and doesn't require any mechanism to get
initialized, other than this construct.

Richard Shann