c:\dev>perl search_and_replace.pl
Global symbol "$directory" requires explicit package name at search_and_replace.pl line 33.
Execution of search_and_replace.pl aborted due to compilation errors.

##</code><code>##

c:\dev>perl search_and_replace.pl
Path::Tiny paths require defined, positive-length parts at search_and_replace.pl line 33
##</code><code>##

c:\dev>perl search_and_replace.pl
Variable "$path" is not imported at hornbach_mit_verz_suche.pl line 34.
        (Did you mean &path instead?)
Global symbol "$path" requires explicit package name at search_and_replace.pl line 34.

##</code><code>##

c:\dev>perl search_and_replace.pl
': Filename too long at search_and_replace.pl line 34.

##</code><code>##

use 5.014;
use strict;
use warnings;
use File::Slurp qw(:all);
use Path::Tiny qw/ path /;
use POSIX();
use autodie qw/ close /;

my $infile_paths = 'C:\temp\test_folder\paths.txt';

my @paths = read_file $infile_paths, { binmode => ':utf8' } or die $!;
chomp(@paths); 

# say for @paths; 

foreach my $path (@paths){
	Main($path),
} 


Main( @ARGV );
exit( 0 );

sub Main {
	my $directory = "";
    my $date      = POSIX::strftime( '%Y-%m-%d', localtime );
    my $bak       = "$date.bak";
    my @xml_files = path( @paths )->children( qr/\.xml$/ );
    for my $file ( @xml_files ) {
        Replace( $file, "$file-$bak" );
    }
} ## end sub Main

sub Replace {
    my( $in, $bak ) = @_;
    
    path( $in )->move( $bak );
    
    my $infh  = path( $bak )->openr_raw;
    my $outfh = path( $in )->openrw_raw;
    
    while( <$infh> ) {
        s{&}{&amp;}g; ## will match more than what you want fix it
        s{&amp;amp;}{&amp;}g;
        s{\s>\s}{&gt;}g;
        s{\s<\s}{&lt;}g;
        print $outfh $_;
    }
    
    close $infh;
    close $outfh;
} ## end sub Replace