# OPEN,CLOSE,GROUPP ...are numbered at compile time.
OPEN num 1 Mark this point in input as start of #n.
CLOSE num 1 Close corresponding OPEN of #n.
+ SROPEN none Same as OPEN, but for script run
+ SRCLOSE none Close preceding SROPEN
REF num 1 Match some already matched string
REFF num 1 Match already matched string, folded using