sub create_db_install_val(){
  $File_name="DB_INSTALL_VALIDATION.sh";
  print "\n Shell name to validate DB Installation Completion is $File_name\n";
  $MYSCRIPT=<<SCRIPT;
#!/bin/sh
FILE="/scratch/pratranj/DB_11.2.0.1.0/config/setup.log"
STRING="Completed creating database instance"
EXIT=1
while : ;do
  [[ -f "\$FILE" ]] && grep -q "\$STRING" "\$FILE" && echo "DB Installation is completed" && break
  sleep 5
done
SCRIPT

  open (FILE,">$File_name") or die "cannot open $File_name file";
  print FILE $MYSCRIPT;
  close(FILE);
}

Output:
-------
$ cat DB_INSTALL_VALIDATION.sh
#!/bin/sh
FILE="/scratch/pratranj/DB_11.2.0.1.0/config/setup.log"
STRING="Completed creating database instance"
EXIT=1
while : ;do
  [[ -f "$FILE" ]] && grep -q "$STRING" "$FILE" && echo "DB Installation is completed" && break
  sleep 5
done