Be careful of uninstallation. I wouldn't recommend it. What I would do is:
perl Build.PL wxWidgets-version=2.9.4
I use CPAN. Did you know that you can configure CPAN to uninstall for you? It'll uninstall conflicting files, but don't use it if you use INSTALL_BASE. Enter the CPAN shell:
cpan> o conf init mbuild_install_arg
cpan> --uninst 1
cpan> o conf commit
Check that the change took effect:
cpan> o conf mbuild_install_arg
mbuild_install_arg [--uninst 1]
Now do
cpan> o conf init make_install_arg
cpan> UNINST=1
cpan> o conf commit
cpan> o conf make_install_arg
make_install_arg [UNINST=1]
It worked. You're done. Now install Wx.
Update: Revised