Function num_to_string_for 

pub fn num_to_string_for(n: Num, legacy_float: bool) -> String

Variant for ≤5.2: those dialects only had lua_Number (a double), so PUC’s %.14g formatter trims any trailing .0 (an integer-valued float renders as plain 2, not 2.0). 5.3+ introduced the integer subtype and the renderer started appending .0 to distinguish floats — pm.lua’s pattern transformations build "%" .. (s+1) and need "%2" on 5.1/5.2.