Make a bitset to store all lowercase letters and another for all uppercase letters.
Use union to make a bitset storing all alphanumerical characters.
Use union to make a bitset storing all characters used in hexadecimal numbers.
Make a rules pattern integer to match with integer numbers, starting optionally with a + or - sign.
Make a pattern that matches the following product codes: "#ABC-nnnn" or "#XYZ-nnnn", where nnnn is a four-digit pattern.
Try for yourself to parse the data string to extract the exchange rate0.81191502. (Hint: use some and the letter charset.)
Starting with rate: "<title>1 USD = 0.81191502 EUR</title>", change both tags to <rate> tags, by using two rules.
Use parse and the code within it to obtain the ...
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