I would probably try this, although I am not sure if it's the fastest. :

#
# This function splits a string into
# an array along new-line \n characters.
# Usage: ARRAY = SplitLine(STRING)
# (Tested with TinyPerl 5.8 running on Windows 7.)
#
sub SplitLine
{
  defined $_[0] or return ();
  my ($i, $j, $n, @A) = (0, 0, 0);
  while (($i = index($_[0], "\n", $i)) >= 0)
  {
    $A[$n++] = substr($_[0], $j, $i - $j);
    $j = ++$i;
  }
  $A[$n] = substr($_[0], $j, length($_[0]));
  return @A;
}
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_{Perl is beautiful.}