Variable

Variables

The assigned variable is always the name of the new variable.

Evaluate

Uses (multiple) other variables and evaluates their values to assign the new variable).

Regular expression

Uses a match group to extract a text from an input, e.g.: prefix(.*?)suffix

the non-greedy regular expression returns the inner text between prefix and suffix.

Spring EL

Spring expression language for advanced cases, see Spring Documentation or some tutorials like this.

Remove variable

Variables can also be removed, this is useful to clear state that is not needed anymore or to reset memory, e.g. to remove the context after multiple rounds of conversation.