You can do it the same was way, almost, as the CGI and you should probably modify your CGI call. Something like this–

my %vars = ( cgi => CGI->new(),
             dbh => DBI->connect([connection params]),
           );
[download]

You can just follow the regular docs for those modules then. It's sometimes terribly convenient to code DB calls and such inside templates (hence PHP's rapid rise) but it's usually a bad long term design choice.