perl - Use of uninitialized value $elements[6] in pattern match (m//)

Question

I am trying to run a MitoSite software which is written in Perl. I am not very familiar with perl scripting, and I get the following error:

needLargeMem: trying to allocate 0 bytes (limit: 100000000000)
Use of uninitialized value $elements[6] in pattern match (m//) at MitoSAlt1.1.pl line 221, <CONFIG> line 75.

I guess I have to change something in this piece, but I have no clue since I do not understand it well.

sub check_paired{
  my $check_paired = 0;
  my $path = shift;
  my $line = `zcat $path|tail -n 1`;
  my @elements = split(//, $line);

  $check_paired = 1 if $elements[6]=~m//.$/;
  return $check_paired;
}

question from:https://stackoverflow.com/questions/66064793/use-of-uninitialized-value-elements6-in-pattern-match-m

Answer 1

The "uninitialized" message is a warning that means that the @elements array has fewer than 7 items in it. You could avoid that warning by checking how many items are in the array before you check the item at index 6:

sub check_paired{
  my $check_paired = 0;
  my $path = shift;
  my $line = `zcat $path|tail -n 1`;
  my @elements = split(//, $line);

  if (@elements > 6) {
      $check_paired = 1 if $elements[6]=~m//.$/;
  }
  return $check_paired;
}