Unsuccessful open on filename containing newline at test.pl line 18
This tells you that have to remove the newlines from the lines you are reading from your file list: 
while (<DFFILE>) {
    chomp; # remove newline at the end.
    ($value, $key) = split(/\t/, $_);
    $lijst{$key} = $value;
}

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In reply to Re^3: problem with string substitution output by moritz
in thread problem with string substitution output by Anonymous Monk

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