Then please show us the relevant code+data that produces the output.

I can't reproduce the problem using the following, very short program:

#!perl
use strict;
use warnings;

my $line = "line: label1=N,label2=N,label3=N,label4=NNNNNNNNNNN,label5
+=N,label6=WWWN";

my @data = split(',', $line);
foreach my $datapair (@data) {
   my ($label, $data) = split('=', $datapair);
   print "label: $label; data: $data\n";
   #print OUT1 "$data;";
}

__END__
label: line: label1; data: N
label: label2; data: N
label: label3; data: N
label: label4; data: NNNNNNNNNNN
label: label5; data: N
label: label6; data: WWWN
[download]

... to me, that means, you are either doing something differently in your code that you haven't shown, or your data is something else.