Does this link help?
http://www.webfetch.org/faq.shtml#mod-ro-errWhy does it say "Modification of a read-only value attempted at..."?
This can now be fixed by upgrading to XML::Parser 2.27, which is available at any CPAN mirror or at
http://www.perl.com/CPAN/modules/by-module/XML/perl-xml-modules.html. Alternatively, it can also be fixed by upgrading from Perl 5.004 to Perl 5.005.
We observed this on WebFetch 0.10 using the modules that retrieve news via XML (Slashdot and LinuxToday, so far) while using XML::Parser 2.24-2.26 on Perl 5.004_xx. It was due to a bug in Perl 5.004 which caused a failure in the XML::Parser module, and does not affect Perl 5.005. The changes in XML::Parser 2.27 include a workaround for the Perl5.004 bug.
Before XML::Parser 2.27 was released, we made this patch for XML::Parser 2.26. Now that XML::Parser 2.27 is out, you would only use this patch if, for some reason, you must use Perl5.004_xx and XML::Parser 2.26. It's a fix to the Expat/Expat.xs file, implementing the same workaround for the Perl 5.004 bug as XML::Parser 2.27 uses.