What is the difference between Perl's 'my', 'our', and 'local' variable declarations?

In Perl, the difference between 'my', 'our', and 'local' variable declarations lies in their scoping and visibility.

Focus keyword: Perl variable declarations

'my' keyword:

The 'my' keyword declares a lexically-scoped variable that is only visible within the block it was declared in. This means that variables declared with 'my' are not visible outside of the block in which they were defined.

'our' keyword:

The 'our' keyword declares a package-scoped variable that is visible across different packages. It is similar to 'my' but allows variables to be accessed across different packages within a program.

'local' keyword:

The 'local' keyword declares a dynamically-scoped variable that preserves the value of a global variable within a narrower scope. However, changes made to this variable are not visible outside of the block where it was declared.