Quick question about regex_match

When using regex_match, how would I be able to use the - character? An example of the code is posted below. What would be the correct format? Thanks! 
 

Code:

$rules = [
    'date' => 'required|min_length[2]|max_length[50]|regex_match[/^+[a-zA-Z0-9.- ]+$/]',
];