According to Asterisk wiki: https://wiki.asterisk.org/wiki/display/AST/Pattern+Matching#PatternMatching-SpecialCharactersUsedinPatternMatching

The exclamation mark (!) character is similar to the period and matches zero or more remaining characters. It is used in overlap dialing to dial through Asterisk. For example, _9876! would match any number that began with 9876 including 9876, and would respond that the number was complete as soon as there was an unambiguous match.

Asterisk treats a period or exclamation mark as the end of a pattern. If you want a period or exclamation mark in your pattern as a plain character you should put it into a character set: [.] or [!].

Mc GRATH Ricardo