How to use regex in required_if value in Laravel 4.2

I have 2 field say var1 and var2. both are text fields what I want if var2 contains a word __tocken_ then field var1 is required.

I tried this but it is not working,

$validator = Validator::make(
    ['var1' => 'required_if:var2,regex:/__tocken_/']
    //['var2' => ['required', 'regex:/__tocken_/']] //<--Regex is working fine here
);

So what I'm doing right now I'm setting a 3rd variable var3 and on form submit I'm doing a JS validation if var2 contains a word with pattern __tocken_ then I'm setting var3 as 1 otherwise 0. And the validation rule is

$validator = Validator::make(
    ['var1' => 'required_if:var3,1'] //working fine
);

So my question is it possible to have regex NOT the exact value in required_if validation rule?

Sample possible value for var2

• Hi __FIRST_NAME__, lorem ispam __tocken_Ur1vG6xK__.
• lorem ispam __tocken_456vG6xK__ lorem __tocken_T57kq6xK__
• lorem ispam.. so on