Here is some code. Both the input and output directories are on the samba mount. Functions 1 and 2 do some string manipulation, but don't touch the file system. The $list_file is a file that starts with a path to a directory and then is a list of files. Thank you for your input.

my $list_file=$ARGV[0];
my $outdir=$ARGV[1];
my $file_name;
my $text;
open LIST,$list_file;
chomp(my $path=<LIST>);
while($file_name=<LIST>) {
  chomp $file_name;
  local $/=undef;
  open INFILE,catfile($path,$file_name);
  $text=<INFILE>
  close INFILE;
  my $string=function1($text);
  function2($text);
  my $bindex=index($text,"<XML_TAG>");
  $text=substr($text,0,$bindex).
      "<XML_TAG>\n".
         $string."\n".
      "</XML_TAG>\n".
      substr($text,$bindex);
  open OUT,'>'.catfile($outdir,$file_name);
  print OUT $text;
  close OUT;  
}
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