To clarify, my comment regarding the bullets was in conjunction to another's response. It probably would have been best to read the comment as a response, since it appears, at least on my display, indented to the aforesaid comment.

I appreciate the response. I am aware of the forum guidelines. But since my question was a very limited subset of data, namely an array, I was just needing a prompt in how to compare a scalar item to the previous item on the stack. The fence post error served as a necessary reminder to debug, as mentioned by the previous comments.

So my code was

@line = split /\r/m, $file;
for my $line (@line) {
my $header = ((split(/\t/, $line))[0]);

##stuck here as I was unsure how to compare $header to previously seen
+ header
}
[download]

So, thanks for your response too. It showed me another way to resolve the issue. Much appreciated.