\

The \ character has three distinct functions in CQL:

1. It indicates certain predefined single-character strings: \n, \t, \r, and \" .
2. If followed by one or more digits, it indicates the value of a capturing group following a ~~ operation. If followed by - and one or more digits, it indicates the capturing group index, the character position where the specified capture group occurred in the target string.
3. Within textual regular expressions, the \ character has special functions. It can be used to escape certain special characters, like [ or *.