/usr/libexec/squid/basic_msnt_multi_domain_auth: Can't locate Authen/Smb.pm in @INC (you may need to install the Authen::Smb module) (@INC contains: /etc/perl /usr/local/lib/perl5/5.18.2/i686-linux /usr/local/lib/perl5/5.18.2 /usr/lib/perl5/vendor_perl/5.18.2/i686-linux /usr/lib/perl5/vendor_perl/5.18.2 /usr/local/lib/perl5 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.18.2/i686-linux /usr/lib/perl5/5.18.2 .) at ./basic_msnt_multi_domain_auth line 32. BEGIN failed--compilation aborted at ./basic_msnt_multi_domain_auth line 32.
What version of squid? Where is your emerge --info? Where is your build log?
Also, please try running perl-cleaner.