Support percentage operations in expressions

Currently, writing an expression like: `299 + 21%` is interpreted as: `299 + 0.21` = `299.21` Expected behaviour: `299 + (299 * 0.21)` = `361.79` Would it be possible to add support for this format in addition and subtraction operations, so percentages are applied relative to the preceding value instead of being converted directly to decimals?