Minimal example of calling the `modexp` precompile (0x05) using Solidity.

ModExp.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.26;

contract ModExp {
    function modExp(bytes calldata base, bytes calldata exponent, bytes calldata modulus) public returns (bytes memory) {
        (, bytes memory result) = address(5).call(abi.encodePacked(base.length, exponent.length, modulus.length, base, exponent, modulus));
        return result;
    }

    function example() external returns (bytes memory) {
        // TypeError: Built-in binary operator ** cannot be applied to types int_const 3 and int_const 1000000.
        // return (3 ** 1000000) % 8191;

        // Returns bytes "0x09af" (== 2479), as expected
        return this.modExp(hex"03", hex"0f4240", hex"1fff");
    }
}