Yeah right, its not in the docs. I just forgot to mention them. But they are inside since ever, since the first hashcat version. The following rules are supported:
#define RULE_OP_REJECT_LESS '<'
#define RULE_OP_REJECT_GREATER '>'
#define RULE_OP_REJECT_CONTAIN '!'
#define RULE_OP_REJECT_NOT_CONTAIN '/'
#define RULE_OP_REJECT_EQUAL_FIRST '('
#define RULE_OP_REJECT_EQUAL_LAST ')'
#define RULE_OP_REJECT_EQUAL_AT '='
#define RULE_OP_REJECT_CONTAINS '%'
#define RULE_OP_REJECT_MEMORY 'Q'
#define RULE_OP_REJECT_LESS '<'
#define RULE_OP_REJECT_GREATER '>'
#define RULE_OP_REJECT_CONTAIN '!'
#define RULE_OP_REJECT_NOT_CONTAIN '/'
#define RULE_OP_REJECT_EQUAL_FIRST '('
#define RULE_OP_REJECT_EQUAL_LAST ')'
#define RULE_OP_REJECT_EQUAL_AT '='
#define RULE_OP_REJECT_CONTAINS '%'
#define RULE_OP_REJECT_MEMORY 'Q'