this is covered in the Tk::callbacks basically you can pass any arguments you want as in: -dropcommand => [\&accept_drop, $drop, $another, $more] and they arrive in the sub accept_drop in @_ as always.

The same can be accomplished with:

[ \&subname, arg1,  arg2, ..]
# or 
[ sub { ... },arg1,  arg2, ..]
[download]

Note the [..] around sub and args: if more than one element is passed Tk will expect an anonymous array with the code reference as first element and arguments following.

Also note that the contents of the [..] are evaluated by perl when the callback is created.

PS see it in action:

perl -MTk -e "tkinit->Button(-text=>'print',-command=>[sub{print join'-',@_},1, 2,3])->pack;MainLoop"

L*