X:\>perl foo.pl
Calling test_function with no arguments:
oops: this function takes exactly one argument at foo.pl line 7
        main::test_function() called at foo.pl line 17
        eval {...} called at foo.pl line 16

Calling test_function with an undefined argument:
oops: argument is not defined at foo.pl line 12
        main::test_function(undef) called at foo.pl line 23
        eval {...} called at foo.pl line 22


X:\>