You can set the number of times a character may match the sequence of characters.
To match all two digit integers, your regular expression would be \d\d, which is the same as [0-9][0-9].
Quantifiers express a pattern like "one digit or more".
Quantifiers and their meanings are listed in the following table.
| Quantifiers | Meaning |
|---|---|
| * | Zero or more times |
| + | One or more times |
| ? | Once or not at all |
| {m} | Exactly m times |
| {m, } | At least m times |
| {m, n} | At least m, but not more than n times |
Quantifiers must follow a character or character class.
For example, \d+ says that match one or more number of digits.