I agree with the prior replies... I'm not exactly sure what you are looking for... I tried out your code on a fairly simple example and it seems to work fine:

#!/usr/bin/perl -w

use strict;

my $e = '\\';  # kind of escape char
my $s = '\'';  # this is a string to use for splitting
my $str = "this \n contains \\'\n new lines " .
  "and single'\nquotes'\n more than\' once";
if( $str =~ m#$/# ) {
  $s .= "$/"; # ?? right so?  
}
my $re = qr/(?<!\Q$e\E)\Q$s\E/;
my @parts = split $re, $str;

print scalar(@parts), "\n";
for ( my $i = 0 ; $i < @parts ; $i++ ) {
  print "$i:  $parts[$i]\n";
}
[download]

gives the following output:

% ./test.pl
3
0:  this 
 contains \'
 new lines and single
1:  quotes
2:   more than' once
[download]

The string was split on '\n, but not \'\n, \n or '.