( Place BEGIN, where you want to jump back and AGAIN after
  a relative jump operator. Just like BSET and BWR. )
: BEGIN, PC ;
: AGAIN, PC - 1- A, ;

: BSET PC SWAP ! ;
: BWR @ AGAIN, ;
( same as BSET, but we need to write a placeholder )
: FJR, PC 0 A, ;
: IFZ, JRNZ, FJR, ;
: IFNZ, JRZ, FJR, ;
: IFC, JRNC, FJR, ;
: IFNC, JRC, FJR, ;