def t_COMMAND(t):
    r'create|show'
    return t

def t_SCOPE(t):
    r'user|domain'
    return t

def t_STRING(t):
    r'[a-zA-Z_@*.]*'
    return t

show user where created_on = foo

S:COMMAND SCOPE FILTER;
FILTER:WHERE EXP |;
EXP:STRING OP STRING
...