sub addem 
{
    my %hash = 
    (
        OPERAND1 => 2,
        OPERAND2 => 3,
        @_,
    );

    return $hash{OPERAND1} + $hash{OPERAND2};
}

print "The result is: " . addem();
print "\n";
print "The result is: " . addem(OPERAND1 => 3);