I didn't test NetWallah's solution, but I thought I'd take a sec to try to help you understand why we know you didn't test your own code, and show you a couple more updated approaches to writing Perl.

You should use the three argument form when opening a file, and be ready to spit the reason if the open fails, like this:

open my $fh, '<', 'list.txt' or die "Can't open list.txt: $!";
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Note that I used a scalar ($fh) to accept the File Handle instead of a bareword ('IN', in this case). The '<' signifies that the file is to be opened in read-only mode.

Also, if you ran your code, you would have found that under the 'strict' pragma, you need to make your declared/defined variables lexical. Most commonly, we'd use 'my' to do so:

my ( $a, @ss ) = split ...
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One last thing... within a while loop when iterating through a file, it is idiomatic to write it like this (note the 'my'):

while ( my $line = <$fh> ){
    chomp $line;
    print "$line\n";
}
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