A similar method is already possible:
Code:
alias moo { 
var %moo = $1 
goto %moo
:cow
echo -a moo cow 
return
:dog 
echo -a moo dog 
return
:cat 
echo -a moo cat 
return
:%moo
echo -a moo mouse 
return 
}

If only women came with popup menus and online help.