bsplinecurve b1 3 3 0 4 3 1 4 4  0 0 0 1  1 2 0 1   2 3 0 1  3 2 0 1   4 0 0 1
copy b1 b2
smirror b2 0 0 0 0 -1 1 
pl
pl
pl
pl
renamevar b2 result
set length 6.6067715112002166