This seems right, the '-a' switch doesn't take wildcards:


      $ whence -a zsh
    /usr/local/bin/zsh
    /usr/bin/zsh
    /bin/zsh

... however the '-m' switch accepts wildcards:


    $ whence -m "zsh*"
    /usr/local/bin/zsh
    /usr/local/bin/zsh-ok
    /usr/local/bin/zsh-test1
    /usr/local/bin/zsh-test2-orig-rebuild
    /bin/zsh4
    /bin/zsh5

... yet, although '/usr/local/bin/zsh' is found, all of the other files 
found by
'whence -a zsh' above are missed. How is it that '/usr/local/bin/zsh' 
matches
'zsh*' but '/bin/zsh' does not?