On $*:TEXT:^(\.c|!c|\.command|!command)$:#help: {
(or) On $*:TEXT:^([.]c|!c|[.]command|!command)$:#help: {
(or) On $*:TEXT:^([.!]c|[.!]command)$:#help: {
(or) On $*:TEXT:^([.!](?:c|command))$:#help: {
echo -a The command $regml(1) was typed.
; note that '.' is a special wildcard character in regex, so it
; must be escaped with '\' or presented inside a character class '[]'
; see how alternation works with pipe '|'
; see how grouping_with_backreference works with '()'
; see how grouping_without_backreference works with '(?:)'
}