regex to check valid email in oracle

Below regex is validating almost all valid and invalid email addresses mentioned at :https://blogs.msdn.microsoft.com/testing123/2009/02/06/email-address-test-cases/

Code:

DECLARE 
    v_email webowner.person.email%TYPE;

    v_constant CONSTANT VARCHAR2(300) := '^(([a-zA-Z0-9"_\-])((\.?[a-zA-Z0-9_\/%+="''\-]+)\.?[a-zA-Z0-9+-]*)@(\[((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}|((([a-zA-Z0-9\-]+)\.)+))([a-zA-Z]{2,}|(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\]))$';
    BEGIN
      v_email := 'email@domain.com';
    if regexp_like(v_email, v_constant) then

      pl('YES: ' || v_email);
    else
      pl('NO: ' || v_email);
    end if;
    END; 

But the condition now arises, it is expecting minimum of 2 characters(in username part before "@") whereas I need to have only one mandatory character.

e.g.

p@domain.com