Go to a subroutine at program line LLLL if X contains the number nn.
Dialect exclusions: Not available in dialects before 10.
Note: Does not pop X
See also GoSubIfXGE, GoSubIfXGT, GoSubIfXLE, GoSubIfXLT, GoSubIfXNE
GoSubIfXGE
GoSubIfXGT
GoSubIfXLE
GoSubIfXLT
GoSubIfXNE