Simple regular expression for a decimal with a precision of 2

Question

What is the regular expression for a decimal with a precision of 2?

Valid examples:

123.12
2
56754
92929292929292.12
0.21
3.1

Answer 1

To include an optional minus sign and to disallow numbers like 015 (which can be mistaken for octal numbers) write:

-?(0|([1-9]\d*))(\.\d+)?