:
s/^\(\w*\)_/\1o/
t
s/_0/9_/
s/[1-9]/&_/g
y/123456789/012345678/
t
:4
s/o\(.*0\(_*\)\)/\2\1/
s/0_\{10\}/_0/
s/^_/0_/
s/^00/0/
t4
s/\(.*\),.*/\1/
//t
s/0_*/&9876543210 /g
s/0.\{9\}\(.\)\w* /\1/g
Note that non-ascii characters in the above source code will be escaped (such as \x9f).