Requested changes

- Removed unneeded @query-ies and return()s
- Added singular/plural
- Added invalid action if statement to /mail
Added [$=''] trick

Added the [$=''] trick. Explaination:
'/ra = foo' will only catch '/ra' and not '/ra invalid param'
'/ra [$=''] = bar' will catch anything that uses '/ra' as the base
command. It will just ignore any extra parameters the player gives. You
could make it drop an error if length($) > 0, but meh.