Triggers execution only when selected prefix is present. For example if exclamation mark ! is the prefix, the command has to start with it in order for it to run.
Takes prefix to be used in the rule. Prefix max length is 100 characters. Please note prefixes are case-insensitive.
Empty prefix is considered valid. In practice this means everything will pass the rule.
This example uses exclamation mark as the prefix.
!custom-command
custom-command
Some other message without prefix.