The circumflex has a second meaning when it is used outside of the brackets. When use the circumflex ^ outside of brackets, it matches the beginning of the line.
The example with the numbers 20-29 should be solvable much shorter, now. Place the circumflex at the beginning of the regular expression to find all numbers starting with 2.
- 12
- 16
- 20
- 24
- 28
- 32
- 36