/^\\d{1,2}(\.\d{1,2})?$/

This regular expression matches a string that starts with one or two digits, followed by an optional decimal point and one or two more digits after the decimal point.

Example matches:

• 4
• 12.5
• 99.99

Example non-matches:

• 0.5 (must have at least one digit before the decimal point)
• 3.456 (only allows up to two digits after the decimal point)
• 12345 (too many digits before the decimal point)