SQL*Plus Conditional Script Execution

plsql_conditional_script_execution.sql

-- activate substitution variables
set define on
-- suppress echo for substitution variables
set verify off
-- activate stdout
set serveroutput on

define _IF_MASTER_INSTANCE="--"
col master_instance new_value _IF_MASTER_INSTANCE  noprint

select case
         when sys_context('USERENV',
                          'DB_NAME') = 'ABCD' then
          'script.sql'
         else
          'noop.sql' -- empty
       end master_instance
  from dual
/


@&_IF_MASTER_INSTANCE

undefine _IF_MASTER_INSTANCE
col master_instance clear