I *do* think that something is wrong with XML in terms of resources. Consider the XML and Storable files generated by this script (note that you should lower the number of records if you are short on RAM as the following tests will take near 1GB of memory or so): 
use constant RECS => 1000000;
{
    open my $fh, ">/tmp/bla.xml" or die;
    select $fh;
    print "<addresses>\n";
    for (1..RECS) {
    print <<EOF;
  <address>
     <name>John Smith</name>
     <city>London</city>
  </address>
EOF
    }
    print "</addresses>\n";
}

{
    require Storable;
    my @addresses;
    for (1..RECS) {
    push @addresses, { name => "John Smith", city => "London" };
    }
    Storable::nstore(\@addresses, "/tmp/bla.st");
}

[download]
Two mostly equivalent data sources. Now the two benchmarks (I am using tcsh's time command here, showing system, user, elapsed time and maximum memory): 
$ ( set time = ( 0 "%U+%S %E %MK" ) ; time perl -MStorable -e 'retriev
+e "/tmp/bla.st"' )
1.980+0.384 0:02.41 193974K
$ ( set time = ( 0 "%U+%S %E %MK" ) ; time perl -MXML::LibXML -e 'XML:
+:LibXML->new->parse_file("/tmp/bla.xml")->documentElement' )
6.037+1.876 0:08.15 643952K

[download]
So naive parsing of XML is much worse in both memory allocation and CPU time than loading the same Storable file. I guess that most other fast serializers like YAML::Syck or JSON::XS will give similar results.

In reply to Re^3: Memory Efficient XML Parser by eserte
in thread Memory Efficient XML Parser by perlgoon

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