DBI consults several environment variables, listed in Table G.4. All of them, except DBI_TRACE, are used by the connect() method. DBI_DRIVER is used by the data_sources() method, and DBI_TRACE is used by trace().
|DBI_DRIVER||DBD-level driver name ("mysql" for MySQL)|
|DBI_DSN||Data source name|
|DBI_TRACE||Trace level and/or trace output file|