#!/usr/local/bin/perl -w
use strict;

chomp(my @lines = <DATA>);
my @newlines = reverse grep m/'\d+'/, @lines;

@lines = map { if (/'(\d+)'/) {
                  my $c = scalar @newlines - $1 + 1;
                  my $l = $1 == 1 ? "NewLine1\n" : "";
                  "$l(+$c) " . $newlines[$1-1] . ";fac=$c"
               } else {
                 /Line5/ ? "$_\nMeanLine" : $_
               }
         } @lines;

print "$_\n" for @lines;


__DATA__
Line1
Line2
Line3
Line4
Line '1'
Line '2'
Line '3'
Line '4'
Line5
Line6

##</code><code>##

Line1
Line2
Line3
Line4
NewLine1
(+4) Line '4';fac=4
(+3) Line '3';fac=3
(+2) Line '2';fac=2
(+1) Line '1';fac=1
Line5
MeanLine
Line6