sudo apt-get install firebird2.1-dev

I have installed latest DBI
wget http://search.cpan.org/CPAN/authors/id/T/TI/TIMB/DBI-1.609.tar.gz
tar -zxvf DBI-1.609.tar.gz
cd DBI-1.609
perl Makefile.PL
sudo make install

Then install the Firebird driver
wget http://search.cpan.org/CPAN/authors/id/E/ED/EDPRATOMO/DBD-InterBase-0.48.tar.gz
tar -zxvf DBD-InterBase-0.48.tar.gz
cd DBD-InterBase-0.48
perl Makefile.PL
make
make test (optional step)
make install