Please, keep in mind that it is Sunday morning here (so I might not think very clearly at the moment).
Although it, probably, is possible in SQL, why wouldn't you do the decision at the operating system level? This script would, using a simple IF-THEN-ELSE call required .SQL script which would then ask for required parameters and do what it needs to do.
SELECT 'This is script 1' FROM dual;
SELECT 'This is script 2' FROM dual;
This is a menu script:
ACCEPT answer PROMPT 'What to do: ';
SET TERMOUT OFF
SET VERIFY OFF
SET HEADING OFF
SET PAUSE OFF
SET ECHO OFF
COLUMN what_to_do NEWLINE;
SELECT DECODE (&answer, 1, '@script_1.sql',
3, 'Wrong answer'
SET TERMOUT ON;
Test it and see how it works; tweak it, adjust it according to your needs, but - basically - it should be OK. Of course, if SQL*Plus commands are allowed (just like William said).