!print backward!
< !forward line! (.-z); .u3 l (.-2)u4 (q4-q3)u1
!print to cr! q3,q4t
!reverse line! (.-z); .u3 l (.-2)u4 (q4-q3)u2
!empty line?! q2"E ;t
 Oend reverse'
!length difference! (q1-q2)u5
!new on longer! q5"L (-q5)<;tx>'
!end forward! ;t
 
!new one shorter! (-q5)"L q5<;tx>'
!print line backward!<(q3-q4); (q4-1)u0 q0,q4t q0u4>
!end reverse! ;t

>
!final CR! ;t