main.rb

Explanation:
- `Math` module is used to get the value of Pi.
- `cylinder_volume` function accepts two arguments - `radius` and `height`.
- The function calculates the volume of the cylinder using the formula `πr²h`.
- The calculated volume is returned by the function.
- The `puts` function is used to output the calculated volume for the given input values of radius=3 and height=5.
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