Sundry Completion Questions ($_ $(^^) $(!!:s//)

[Sonny Michaud <michaud.sonny@gmail.com>]

Good evening!

I have a few questions regarding some different completion mechanisms in 
zsh.

1) I noticed that $_<TAB> does not expand.  I am wondering if other 
parameter substitutions do expand and, if so, if there is an equivalent 
for $_ that is similarly pithy.  If not, is this something that deserves 
a feature request?

2) Quick history substitution does not expand in subcommands.  For 
instance, the following example does nothing.  I am not sure if this is 
also something that would warrant a feature request.
$ touch foo
$ echo $(^touch^cat)

3) Since the above does not work, I usually use $(!!:s/foo/bar), which 
has bizarre behavior, depending on whether or not a trailing slash is 
provided. This one feels like a bug proper, but it may have something to 
do with what I am attempting in particular.

$ grep -r foo
$ vim $(!!:s/-r/-rl)<TAB> -> vim $(grep -rl) foo

whereas

$ grep -r foo
$ vim $(!!:s/-r/-rl/)<TAB> -> $ vim $(grep -rl foo)

If anyone has any thoughts or suggestions about this, I would really 
appreciate the feedback.  Thanks!

- Sonny