/^\d+$/                      # integer
/^\d+(?:\.\d+)?$/            # integer or optional real
/^\d+(?:\.\d\d)?$/           # int or opt. 2-digit float
/^\d+(?:\.(?:\d\d)?)?$/      # int, int with opt '.', or 2-digit float

# Ways of doing optional integer portion (e.g. .12)
/^\d*(?:\.(?:\d\d)?)?$/           # WRONG (matches "")
/^\d+(?:\.(?:\d\d)?)?$|^\.\d\d$/  # better, but still ugly