Regex:
- `^` Line start
- `#*\s*` Find line even if commented out
- `(port)` 'port' -- capture as backreference `\1`
- `\s*=\s*` Equals sign, whether or not surrounded by whitespace
- `\d{4,5}` Existing port value, expected at 4/5 digits
- `(.*)` Remainder (i.e. comment) -- capture as backreference `\2`
- `$` Line end