user
Many language implementations come with an *interactive mode*.

This is a command-line interpreter that reads lines from the user and evaluates these lines as statements or expressions.

An interactive mode may also be known as a *command mode*,   a *read-eval-print loop* (REPL),   or a *shell*.

Task

Show how to start this mode.

Then, as a small example of its use, interactively create a function of two strings and a separator that returns the strings separated by two concatenated instances of the separator   (the 3rd argument).

Example

```
             f('Rosetta',  'Code',  ':')   

```

should return

```
             'Rosetta::Code'               

```

Note

This task is   *not*   about creating your own interactive mode.
assistant
(formerly Perl 6)
Using Rakudo.

```
$ rakudo/perl6
> sub f($str1,$str2,$sep) { $str1~$sep x 2~$str2 };
f
> f("Rosetta","Code",":");
Rosetta::Code
>

```