Overriding virtual methods

Declaration of overriding method should contains specifiers "virtual" and "override" (using Standard_OVERRIDE alias for compatibility with old compilers).
class MyPackage_BaseClass
{
public:
  Standard_EXPORT virtual Standard_Boolean Perform();
};
~~~~~{.cpp}
class MyPackage_MyClass : public MyPackage_BaseClass
{
public:
  Standard_EXPORT virtual Standard_Boolean Perform() Standard_OVERRIDE;
};

This makes class definition more clear (virtual methods become highlighted).