It should work like this:

#!/usr/bin/perl
use warnings;
use strict;

my $echo = 'ECHO';

@ARGV == 2 or die "usage: $0 file1 file2\n";

open DFFILE, '<', $ARGV[ 0 ] or die "$ARGV[ 0 ]: $!";
my @lijst = sort map /^1\t([^\t\n]+)/, <DFFILE>;
close DFFILE;

open LIST, '<', $ARGV[ 1 ] or die "$ARGV[ 1 ]: $!";
chomp( my @listfiles = <LIST> );
close LIST;

for my $word ( @lijst ) {
    for my $file ( @listfiles ) {
        open FILE, '<', $file or die "$file: $!";
        open OUT,  '>', "$file.out" or die "$file.out: $!";
        reset;
        while ( <FILE> ) {
            ?^$word$? or s/$word/$echo/g;
            print OUT;
            }
        }
    }
[download]