: Loop
# All done
/^-*00* /s///
/ -*00*$/s///
t

# Negative Check
/^\(-*\)[0-9].* \1[0-9]/!b Negative

# Create magic lookup table
s/\(.[0-9]*\) \(.[0-9]*\)/\1;987654321000009999000999009909 \2;012345678999990000999000990090/
s/ \(-\)*\(9*;\)/ \10\2/
# Decrement 1st number
s/\([^0]\)\(0*\);[^0]*\1\(.\).*\2\(9*\).* \(.*\)/\3\4 \5/
# Increment 2nd
s/\([^9]\)\(9*\);[^9]*\1\(.\).*\2\(0*\).*/\3\4/
t Loop

: Negative
# Create magic lookup table
s/\(.[0-9]*\) \(.[0-9]*\)/\1;987654321000009999000999009909 \2;987654321000009999000999009909/
# Decrement 1st number
s/\([^0]\)\(0*\);[^0]*\1\(.\).*\2\(9*\).* \(.*\)/\3\4 \5/
# Decrement 2nd
s/\([^0]\)\(0*\);[^0]*\1\(.\).*\2\(9*\).*/\3\4/
t Loop