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Fund.sol

pragma solidity ^0.4.24;

contract Fund {
    address public owner;
    address public exec;
    
    constructor() public {
        owner = msg.sender;
    }
    
    function setProxy(address newExec) public onlyOwner {
        exec = newExec;
    }
    
    function proxy(string funcName, int numArg1, int numArg2, string stringArg1, string stringArg2) public onlyOwner {
        bool result = exec.delegatecall(bytes4(keccak256(abi.encodePacked(funcName))), numArg1, numArg2, stringArg1, stringArg2);
        
        if (!result) {
            revert("Something went wrong during the exec call.");
        }
    }
    
    modifier onlyOwner() {
        require(msg.sender == owner, "This can be only called by contract owner.");
        _;
    }
}

Librarian.sol

pragma solidity ^0.4.24;

contract CommonLib2 {
    string public result;
    
    function word() public {
        result = "hi";
    }
}

contract CommonLib3 {
    string public result;
    
    function word() public {
        result = "bye";
    }
}

contract Fund {
    string public result;
    address public lib;
    
    function setLib(address newAddr) public {
        lib = newAddr;
    }

    function word() public {
        bool success = lib.delegatecall(bytes4(keccak256("word()")));
        
        if(!success) {
            revert('FOOOOOOOOOOOOOOOOOOK');
        }
    }
}