Hello AllPaoTeam, and welcome to the Monastery!

You open INPUT2 for writing, i.e. output, and OUTPUT2 for reading, i.e. input. That’s a confusing way to name your variables!

But the obvious problem is with the first argument to split:

@lines = split /s+/, $t2;
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which says split on one or more lowercase ‘s’ characters. I think you meant:

@lines = split /\s+/, $t2;
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which splits on whitespace. Beyond that, I doubt that we can help much without seeing the input text.

BTW, please consider adopting these best practices:

• use strict; and declare variables with my
• use warnings;
• prefer lexical filehandles: open(my $input2, '>', $file4) or die "Cannot open file '$file4' for writing: $!";

Hope that helps,