[LA.pm] split() question

[Benjamin J. Tilly]

"William Yardley" <lapm at veggiechinese.net> wrote:
> 
> I'm doing some maintenance on a CPAN module I didn't write
> (Mail::DeliveryStatus::BounceParser), and (around line 356 if anyone
> needs to actually look there), we do something like:
> 
> foreach my $para (split /\n{2,}/, $delivery_status_body) {
>        my $report = Mail::Header->new([split /\n/, $para]);
> 
> What's strange, is that in some cases, there is a leading \n left, which
> results in $report not having the stuff we expect there. I'd assume that
> since the \n{2,} should be greedy, there wouldn't be any \ns left after
> that split. However, if I print out $para inside the loop, I see a
> leading \n.

Is it possible that your data looks like "\nstuff\n\n\nmore stuff"?  Then the first string has a \n at the start that the split is not going to catch.

But if the \n is starting on the second string, then that is a bug.  I would create a minimal test example and report it.  Then workaround the bug in any way you can.

> Simply doing a:
>        $para =~ s/\A\n+//g;
> in between those two lines "fixes" the problem - but I was wondering if
> anyone know why this is happening.

You have my top two guesses in order.  First, $delivery_status_body sometimes starts with \n, and failing that that there is  Perl bug.  The third most likely possibility is that you have a Heisenbug, which you'd notice by your inability to produce a minimal test case.  I have no useful suggestions for what to do then.

Cheers,
Ben