s/x$\|x*[+-][^x]*$//
:
s/[1-9]/&=/g
s/\(\^.\)=/\1~/g
y/123456789/012345678/
t
s/=\([^~]*\(~\+\)\)/\2\1/
s/0~\{10\}/~0/
t
y/=/~/
s/\^0~/^/g
s/~\+/&987654321 /g
s/0\?~.\{8\}\(.\)\w* /\1/g
s/\^1//