[scott@blast test]$ ./test.pl
0, -0/0_test.txt-
Use of uninitialized value in concatenation (.) or string at ./test.pl line 7.
1, --
2, -2/2_test.txt-
Use of uninitialized value in concatenation (.) or string at ./test.pl line 7.
3, --
4, -4/4_test.txt-