Passing Command Line Parms to Anonymous Procedures in an SQLPLUS script

Can this be done? The documentation is not clear.

Example

SQL > @my_script.sql parm1 parm2

my_script.sql

set serveroutput on

declare

vparm1 varchar2(20) := parm1 -- initalize a variable with the parameter from command line
vparm2 varchar2(20) := parm2 -- initalize a variable with the parameter from command line

--
begin

dbms_output.put_line('First paramater is '||vparm1);
dbms_output.put_line('Second paramater is '||vparm2);

end;

Thanks,

Don Hall