How to display the currently used ORACLE_HOME from sqlplus

Thanks to my former colleague Laurent Schneider for pointing out a way to display the currently used ORACLE_HOME from within sqlplus:

set lines 200
col oracle_home format a40
set autoprint on
var oracle_home varchar2(255)
exec dbms_system.get_env('ORACLE_HOME',:ORACLE_HOME);

PL/SQL procedure successfully completed.

ORACLE_HOME
------------------------------

/u01/oracle/product/11204

Note: To automatically display the value of a bind variable created with VARIABLE, use the SET AUTOPRINT command.
ON or OFF controls whether SQL*Plus automatically displays bind variables (referenced in a successful PL/SQL block or used in an EXECUTE command).

Source: Oracle Documentation