% cat simple.pl
#!/usr/bin/perl
use DBI;
my $dsn="dbi:ODBC:driver={ODBC Driver 11 for SQL Server};server=tul1system;database=Mosaic"; # SOLVED: keyword "DRIVER=" needs to be all caps
my $dbh = DBI->connect($dsn, "user334", "2BEvPog");

if (! defined($dbh) ) {
	print "***Error connecting to DSN\n";
	print "***Error was:\n";
	print "***$DBI::errstr\n";         # $DBI::errstr is the error
}

% simple.pl
DBI connect('driver={ODBC Driver 11 for SQL Server};server=tul1cspeldb02;database=Mosaic','user334',...) failed: [unixODBC][Driver Manager]Data source name not found, and no default driver specified (SQL-IM002) at ./simple.pl line 6
***Error connecting to DSN
***Error was:
***[unixODBC][Driver Manager]Data source name not found, and no default driver specified (SQL-IM002)