Are you perhaps trying to compile DBI with Sun's Forte C compiler
? I can't be sure, because you didn't include the rest of your error messages. They would have been very helpful. However, since you are on Solaris, I suspect that there's a pretty good chance that your version of perl was not compiled with the same compiler that you are trying to build DBI with.
You need to build the DBI module with the same compiler that Perl was built with. Try running the command "perl -V" (capital V) for more information on the compiler that was used. There is alot about this on Google also.
Updated: Changed to indicate capital V for the perl -V command.