Thanks for your effort in understanding my problem here. I tried your code, its works perfectly fine for the example which i had posted. I didnt understand this part

foreach (@aListMembers) {
    #we only care if its longer than what we already have
    if (exists($hLongest{$_})) {
      my $kLists = $hLongest{$_};
      my $aList = $hLists{$kLists};
      next if ($iCount <= scalar(@$aList));
    }
[download]

hLongest is empty, how can we find if exists here? moreover, when i added a line to the input file like this:

mylist_12 sublist153  sublist_34 sublist_123 sublist_345 sublist_245
mylist_1  sublist_153  sublist_87  sublist_876  sublist_78
mylist_6  sublist_8
mylist_2  sublist_12  sublist_34  sublist_09
mylist_3  sublist_87  sublist_09
mylist_7  sublist_8  sublist_9
mylist_9  sublist_56 

the result should be:
mylist_12 sublist_153  sublist_34 sublist_123 sublist_345 sublist_245
mylist_2  sublist_12  sublist_34  sublist_09
mylist_7  sublist_8  sublist_9
mylist_9  sublist_56 

but in the result, even the shorter line which has sublist_153 gets ad
+ded to result like this:

mylist_12 sublist153  sublist_34 sublist_123 sublist_345 sublist_245
mylist_1  sublist_153  sublist_87  sublist_876  sublist_78
mylist_2  sublist_12  sublist_34  sublist_09
mylist_7  sublist_8  sublist_9
mylist_9  sublist_56 

In the above result, sublist_153 is present in 2 lines.
[download]

In my final output, all the lines should be unique. All the lines in the output file shouldnt have anything in common. In your program, Are you comparing each element in each line, with each element in other lines ???? can we arrange the lines by descending order first, and then start searching "one line" with all the other lines in the file. In that case, when a match(common elements) of that "one line" in present in some other lines, all the other lines having a duplicate element can be deleted. We need not worry about the length, because, the "one line" will always be longer than the other lines in the file since we have sorted it by length in decending order. So, when we read through the whole file, "one line" would be the current line in side a foreach loop or while loop, and we will encounter only the left out lines( because, we will delete the duplicate lines when we find them while matching/looking for common elements). Hope my explanation is clear to you. Thank you once again for your kind help :)

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