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

my $start_flag = '<REANALYZED>';
my $stop_flag = '</REANALYZED>';
my $replacement = <<'REPL';
    "z:\path\newfilename1.ext" GL
    "z:\path\newfilename2.ext" GL
    "z:\path\newfilename3.ext" GL
    "z:\path\newfilename4.ext" GL
    "z:\path\newfilename5.ext" GL
    "z:\path\newfilename6.ext" GL
REPL

open ORIGINAL, "< original.txt"
    or die "can't open original file\n";
my $original;
{
local $/;
$original = <ORIGINAL>;
}
close ORIGINAL;

$original =~ s/
    $start_flag
    .*?
    (\s*)
    $stop_flag
    \n
    /$start_flag\n$replacement$1$stop_flag/gsx;

open COPY, "> copy.txt"
    or die "can't write to copy\n";
print COPY $original;
close COPY;