What are Metavariables in Programming?

In programming, a metavariable is a variable that is used to store information about other variables. It is a variable that is used to keep track of the state of other variables, rather than storing a value itself.

For example, in a programming language that supports meta-programming, you might use a metavariable to keep track of the number of times a particular function has been called, or to store information about the type of data that a variable is holding.

Metavariables are often used in combination with reflection, which is the ability of a program to examine and modify its own structure and behavior at runtime. By using metavariables, you can write code that is more flexible and adaptable, and that can be easily modified or extended at runtime.

Here's an example of how you might use a metavariable in Python:
```
class MyMetaClass(type):
__metacount = metavariable.Variable('int')

def __init__(self, *args, **kwargs):
self.__metacount = 0
super().__init__(*args, **kwargs)

def my_method(self):
self.__metacount += 1
print(f'{self.__class__.__name__} called {self.__metacount} times')
```
In this example, the `MyMetaClass` class has a metavariable called `__metacount` that is used to keep track of the number of times the `my_method` method is called. The `my_method` method increments the value of `__metacount` each time it is called, and prints out the name of the class and the number of times the method has been called.

You can use metavariables in a similar way to use variables in your code, but they are more powerful because they can store information about other variables. This makes them useful for creating flexible and adaptable code that can be easily modified or extended at runtime.