cache::async 0.3 has a critical bug.
By running the following code

-----------------------------
package require cache::async

proc myDataFetcher args {  }

cache::async myDataProvider myDataFetcher
myDataProvider clear KEY
--------------------------------------------

.. an error is raised

errorInfo: can't read "arg": no such variable
    while executing
"llength $arg"
    (procedure "::cache::async::Snit_methodclear" line 18)
    invoked from within
"myDataProvider clear KEY"


Fixing the bug only requires to correct "arg" in "args".

I included a zip with all the updated files
- async.tcl     --  the main correction, and version changed to 0.3.1
- pkgIndex.tcl  --  version changed from 0.3 to 0.3.1
- async.test    --  added 2 testcases

ABU