It would, but how in test.pl can I tell that 'DBI' was specified on the command line? test.pl needs to know that.

Yes, and this is Perl ;)

perl -MDBI -le'print for keys %INC'
Exporter.pm
Carp.pm
strict.pm
vars.pm
Config.pm
warnings/register.pm
warnings.pm
DynaLoader.pm
Exporter/Heavy.pm
DBI.pm
AutoLoader.pm
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