| ⊦ flatten(val ++ stringval(`')) = flatten(val) ++ stringval(`') |
is_valuelist(val) ⊦ flatten(val ++ stringval(`')) = flatten(val) ++ stringval(`')
⊦ is_valuelist(val), flatten(val ++ stringval(`')) = flatten(val) ++ stringval(`')
[[CONCRETESIMPRULES : ()], [EXTRAFMAS : (is_valuelist(val))]]