If you used apt-get/rpm/whatever to install perl, you use apt-get/rpm/whatever to uninstall perl :)

If you did not, you use rm -rf, usually rm -rf /usr/local/perl5 or whatever is in @INC (or whatever is specified in  perl -V:install.*)

Or see the .packlist file in perl -V:archlib for a core list of files installed with perl

Since you installed over an existing install, maybe you simply need to trim @INC/PERL5LIB or rearrange $PATH, it depends if perl -V:install.* doesn't include version specific directories (with 5.12.3 in the name)

Maybe you simply need to reinstall the old version :) These might be relevant

• (Help Needed) Uninstall Perl 5.10 and Install 5.8 on Ubuntu 10.04
• Uninstalling / installing perl