Hi experts,

I faced with the following error during running the perl script. As I searched on net, it's one of common perl error. Although I tried hard to solve the error with searching on net, I was not successful at all as I'm really new in this field, so your help would be highly appreciated.
The parts of error is here (the error was big and sounds that for all lines)

Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 01.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 03.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 35.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 75.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 81.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 85.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 87.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 89.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2661 93.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2662 37.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2662 63.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2663 59.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2663 83.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2663 97.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2665 45.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2671 05.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2671 07.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2673 17.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2674 87.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2676 63.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2677 41.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2678 53.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2678 55.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2684 93.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2695 83.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2696 51.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2697 15.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2697 21.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2697 49.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2698 09.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2699 15.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2705 53.
Use of uninitialized value in concatenation (.) or string at sequence_replacement.pl line 56, <TWO> line 2706

Thanks so much in advance.

Showing us the error is kind of pointless if you do not show the corresponding code causing it.