The first thing to say is that that is not valid XML. (A valid XML document must contain a single top level tag.)

That said, for the purposes of processing, that (arbitrary) XML rule works in our favour and makes writing a program that processes the large file in smallish chunks very simple:

#! perl -slw
use strict;
use XML::Simple;
use Data::Dump qw[ pp ];

$/ = '</object>';
while( <DATA> ) {
    last if /^\n+$/;
    my $xml = XMLin( $_ );
    pp $xml;
}




__DATA__
<object some_param="abc" other_param="def">
  <attrib1>val1</attrib1>
  <attrib5>val3</attrib5>
</object>
<object some_param="xxx">
  <attrib3>valx</attrib3>
  <attrib7>valy</attrib7>
</object>
<object some_param="xyz">
  <attrib1>valx</attrib1>
  <attrib2>valy</attrib2>
  <attrib3>valx</attrib3>
  <attrib4>valy</attrib4>
  <attrib5>valx</attrib5>
  <attrib6>valy</attrib6>
  <attrib7>valx</attrib7>
  <attrib8>valy</attrib8>
</object>
[download]

That produces:

C:\test>t-XML.pl
{
  attrib1     => "val1",
  attrib5     => "val3",
  other_param => "def",
  some_param  => "abc",
}

{ attrib3 => "valx", attrib7 => "valy", some_param => "xxx" }

{
  attrib1    => "valx",
  attrib2    => "valy",
  attrib3    => "valx",
  attrib4    => "valy",
  attrib5    => "valx",
  attrib6    => "valy",
  attrib7    => "valx",
  attrib8    => "valy",
  some_param => "xyz",
}
[download]

In addition to that allowing the huge file to be processed very quickly in minimal memory, it would -- were the processing requirements of the individual chunks sufficiently taxing to warrant it -- enable multiple individual chunks to be processed in parallel with threading very easily.

But, if the example is anything like representative of the actual data, that above code will probably allow the entire file to be processed sufficiently quickly -- in a very casual test; less that 2 minutes -- that the need for considering threading disappears completely. The saving coming simply from processing the file in small chunks rather than en masse.

Hello grizzley.

namely he reads the file into memory, does alterations to some params and writes back to another file.

I guess he is using twig_roots and "twig_print_outside_roots=>1" for that. And I was thinking of Template Tool Kit when I read this post.

regards.