You Don't want to uninstall Perl 5.10.x that ships with Ubuntu. That's the system Perl. Don't touch it. If you want to run another version of Perl download it and install it to another path:

./Configure -des -Dprefix=$HOME/Your/other/path/here
make test
make install
[download]

Update: Different major versions or Perl aren't binary compatible, (e.g. 5.8.x to 5.10.x), you can't expect modules with aren't pure Perl to work without reinstalling said modules.

The simplest way to correct the problem is to reinstall BugZilla. Most probably your new 5.10 install don't see your old 5.8 modules.

Indeed. It looks like, for one, the module Digest::SHA is missing.

You could also just try to install that one manually module, either via the Ubuntu "install software" feature, or directly in Perl using CPAN. Repeat if you find one more module missing.

If you upgrade the packages for the Perl modules that are failing that will probably solve your problem. You shouldd also check to see if there's a Bugzilla upgrade for 10.04 as well; if there is, it will probably fix all the problems for you. Make sure to back up your bug database before trying a reinstall!

If you installed Bugzilla and its support by hand - that is, you used the CPAN shell or something similar, then that's the reason the Perl modules didn't upgrade - the package management system had no way to know there were Perl modules that wouldn't work with the new Perl. You'll need to rebuild those modules and reinstall them.

Thanks to all of you for posting on this issue. As per suggestion, I installed Perl 5.12.2 on my box in different directory, but running command "perl -v" still shows perl 5.10.1. I tried to run "perl -V" and it displays error message as

 perl -V
Can't locate Config.pm in @INC (@INC contains: /etc/perl /usr/local/li
+b/perl/5.10.1 /usr/local/share/perl/5.10.1 /usr/lib/perl5 /usr/share/
+perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_per
+l .).
BEGIN failed--compilation aborted.
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 root@cvsnew:/var/www/bugzilla-3.4# perl checksetup.pl
Can't locate strict.pm in @INC (@INC contains: /etc/perl /usr/local/li
+b/perl/5.10.1 /usr/local/share/perl/5.10.1 /usr/lib/perl5 /usr/share/
+perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_per
+l .) at checksetup.pl line 45.
BEGIN failed--compilation aborted at checksetup.pl line 45.
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root@cvsnew:/var/www/bugzilla-3.4# ./checksetup.pl --check-modules
Can't locate strict.pm in @INC (@INC contains: /etc/perl /usr/local/li
+b/perl/5.10.1 /usr/local/share/perl/5.10.1 /usr/lib/perl5 /usr/share/
+perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_per
+l .) at ./checksetup.pl line 45.
BEGIN failed--compilation aborted at ./checksetup.pl line 45.
root@cvsnew:/var/www/bugzilla-3.6# /usr/bin/perl install-module.pl --a
+ll
Can't locate strict.pm in @INC (@INC contains: /etc/perl /usr/local/li
+b/perl/5.10.1 /usr/local/share/perl/5.10.1 /usr/lib/perl5 /usr/share/
+perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_per
+l .) at install-module.pl line 22.
BEGIN failed--compilation aborted at install-module.pl line 22.
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I have no idea about how to progress on this issue. Kindly help me out.

If you type:

which perl

You'll notice it returns:

/usr/bin/perl

Which is why you are getting the 5.10 results. If you type:

/your/install/path/here/bin/perl -V

You should see the results for 5.12. In the checksetup.pl script change the shebang line to point to your version of perl. You could create a symlink to your perl install to make things easier.