s%^%h\
s/\\\\/\\\\\\\\/g\
s/\\\
/\\\\\\\
/g\
s/\%/\\\\\%/g\
s/^/s\%^\%/\
s/$/\%/\
p\
g%
h
s/\\/\\\\/g
s/\
/\\\
/g
s/%/\\%/g
s/^/s%^%/
s/$/%/
p
g