CategorialRule

Number of items this transform is used

string or string format of regexp to match data against. To use a regular expression, start and end the string with a slash, '/'. Options can be appedended, notably 'i' for case insensitive matching. The first captured group can be used in the group, see below. Examples

1. 'hello' matches 'hello', not 'hello world'
2. '/hello/' matches 'hello world', but not 'Hello world'
3. '/hello/i' matches 'I say Hello'

Name of the group this is mapped to. The special substring $1 is replaced by the first captured group, in example 4 above, with group set to 'He says $1', the match results in 'He says goodbye'