Scope issues of variables defined in shell functions

The scope of a variable defined outside a function starts from where it is defined and ends where the shell ends or is explicitly deleted.
The scope of variables defined within a function starts from where it is called and ends where the shell ends or is deleted explicitly.

A very simple example illustrates the problem:

	#!/bin/bash
	func_(){
    
    
	    var1='123'
	}
	func_
	echo $var1

Output results

123

Therefore, after a function is called, variables defined within the function still exist after leaving the function.
This problem can easily lead to bugs in the program, so please pay more attention.