SQL & PL/SQL :: Testing Nested Blocks But Logic Is Apparently Not Correct?

I am testing nested blocks, but my logic is apparently not correct.

I am running this script:

DECLARE
v_one number(1) := 1;
v_two number(1) := 2;

[Code]....

I receive the output from only one of the nested blocks:

bad
PL/SQL procedure successfully completed.

SQL>

I understand that I don't need nested blocks for the example above, but this was just a condensed version of what I'm trying to do. I think nesting blocks will be easier to read and maintain, instead of having a huge CASE statement.

How can I execute only the nested block for which the condition is true and ignore the nested blocks that follow?

Are nested blocks not the correct answer here? Should I be looking at invoking procedures/functions instead?