SQLPlus is trying to drop package twice - sql

Question

While executing scripts in SQLPlus I've encountered a problem:
script.sql contains the following lines
#some_pkg.pks
#some_pkg.pkb
drop package some_pkg;
/
After calling
> sqlplus user/password#dbname #script.sql
the following messages are in console:
Package created.
Package body created.
Package dropped.
drop package some_pkg;
*
ERROR at line 1:
ORA-04043: object SOME_PKG does not exist
Please, explain what's happening here. Looks like the package is being dropped twice. Is it possible to avoid the error?

Answer 1

The rules of SQLplus command execution basically are:
Execute the current text when you encounter a semi-colon. Thus if a line doesn't end with a semi-colon, the current text continues to be collected.
If you encounter DECLARE or BEGIN, collect all the text and do not execute on semi-colons
If you encounter a slash (/), execute the collected text.
So what happens in your cases is, that both the semi-colon and the slash execute the DROP statements.
To fix it, remove the slash.
You only need the slash if you have a block of PL/SQL, which always with an END statement. Use semicolons for everything else.
Note: the above rules are simplified. It's more complex in practice.

Answer 2

Some examples will help to understand rules:
Below code will be executed once
begin
dbms_output.put_line('executed');
end;
/
Below code will not execute (missing semicolon)
begin
dbms_output.put_line('executed')
end
/
Below code will be executed twice
begin
dbms_output.put_line('executed');
end;
/
/
Below code will be executed once
select 1 from dual
/
Below code will be executed once
select 1 from dual;
Below code will be executed twice
select 1 from dual;
/