Binary Addition!
 
Basic ideas:  
 
If we start on a blank, scan right
If we start on a '+', jump to "wrapup"
 
Scan past 0/1 to right for '+'.  When located, erase it, move to left,
record the next digit in state, and replace that with a new +.
 
Then scan right for end of both digit strings.  Using state and final '01',
record an "A" or "B" representing 0/1 resp.  
 
If necessary, carry a one into the 0/1s.   Now scan left, past plus.
Start from beginning.
 
Wrapup:
delete the plus and scan right for A/B, converting A/B to 0/1.
Finish on final blank.
 

?(0  0R	If we start on a blank, scan right
 
(0000R		Scan past 0/1 to right, stopping at '+'
(0110R
 
(0++DL		Found '+' -- extend it to left, recording that digit.
 
(D++DL
(D0+AR		Reinstate plus and remember bit in A/B state.
(D1+BR
 
(A++AR		Head back to second number and past to end of digits.
(A11AR
(A00AR
 
(B++BR		Head back to second number and past to end of digits.
(B11BR
(B00BR
 

(A  EL		Stop and reverse (states E/F) at end.
(AAAEL
(ABBEL
 
(B  FL		Stop and reverse (states E/F) at end.
(BAAFL
(BBBFL
 
(E0ALL		0+0=0 and loop
(E1BLL		0+1=1 and loop
(F0BLL		1+0=1 and loop
(F1ACL		1+1=0 and carry
 
(C01LL		carried through and go back to loop.
(C10CL		keep carrying...
 
(E+ADL		Adding new digits.
(F+BDL
(C+1DL		Carried to left end, loop.
 
(L00LL		Loop past start of 2nd number...
(L11LL
(L++DL
 
(D  SR		Must have been looping -- we ran out of digits!
 
(S+ SR		Clean up '+'s
(S00SR		Pass any digits
(S11SR
(SA0SR		Decode A/B to 0/1
(SB1SR
(S  HL		Halt on final digit.