existing variable: $get_var('test_x')
missing variable with default: $get_var('crap', 'default text')
missing variable with default array: $get_var('crap', [])
## we don't support dictionary literals yet
##missing variable with default dict: $get_var('crap', {})
has missing variable? $has_var('crap')
has existing variable? $has_var('test_x')
