Course of Raku / Advanced / Containers / Special and dynamic variables 🆕 / Exercises

A dynamic variable

Problem

A dynamic variable — one written with the * twigil — is looked up by searching outward through the call stack, not by lexical scope. So the value a subroutine sees depends on who called it, which lets a block run the code it calls under a different identity.

1. Declare a dynamic variable $*user with the value 'guest'.
2. Write a subroutine whoami that prints running as followed by the current $*user (for example, running as guest). It must read $*user directly — it takes no parameters.
3. Call whoami once at the top level: it reports guest.
4. Then, inside a block that redeclares $*user as 'admin', call the same whoami again: it now reports admin.

Example

The program prints:

running as guest
running as admin

Solution

✅ See the solution

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