Repeating -warnings increases the warning level, i.e. more warnings are printed. At the end, it will print a status message indicating the number of errors found.
Directories are ignored, an appropriate warning message is printed.
The status 2 indicates that at least one of the specified files does not contain any POD commands. Status 1 overrides status 2. If you want unambigouus results, call podchecker with one single argument only.