Fix CVE-2021-22204:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-22204

Patch extracted from commit cf0f4e7dcd024ca99615bfd1102a841a25dde031
from upstream source repository:

https://github.com/exiftool/exiftool/commit/cf0f4e7dcd024ca99615bfd1102a841a25dde031#diff-fa0d652d10dbcd246e6b1df16c1e992931d3bb717a7e36157596b76bdadb3800

diff --git a/lib/Image/ExifTool/DjVu.pm b/lib/Image/ExifTool/DjVu.pm
index c284d10..03b3f9f 100644
--- a/lib/Image/ExifTool/DjVu.pm
+++ b/lib/Image/ExifTool/DjVu.pm
@@ -18,7 +18,7 @@ use strict;
 use vars qw($VERSION);
 use Image::ExifTool qw(:DataAccess :Utils);
 
-$VERSION = '1.06';
+$VERSION = '1.07';
 
 sub ParseAnt($);
 sub ProcessAnt($$$);
@@ -227,10 +227,11 @@ Tok: for (;;) {
                 last unless $tok =~ /(\\+)$/ and length($1) & 0x01;
                 $tok .= '"';    # quote is part of the string
             }
-            # must protect unescaped "$" and "@" symbols, and "\" at end of string
-            $tok =~ s{\\(.)|([\$\@]|\\$)}{'\\'.($2 || $1)}sge;
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