sqlplus and using the slash as login and password

The following portion of a shell script used to work until we moved/changed environments. What makes the slash in the sqlplus command work? It is now saying invalid login and password when I run the shell script.

I'm referring to: sqlplus /

Here's the portion of code:

while (1)

   $ORACLE_HOME/bin/sqlplus / <<EOF ;
   set serveroutput on size 50000
   SELECT TO_CHAR(SYSDATE,'Dy DD-Mon-YYYY HH24:MI:SS') FROM DUAL;    begin
   pack_report_utils.trawl_for_reports($$,$COUNTRY_CODE);    commit;
   end;
   /
   exit
   EOF

	  wait
		 sleep 300

		 end