use warnings;
use strict;

while (my $fs = <DATA>) {
    if ($fs =~ m{(?i)^/(?:oracle|db|db2|informix|data)(?:\s+\z||\s+\w+\z)} ) {
        print "match: $fs";
    }
}

__DATA__
junk
/oracle
/db
/db2
/informix
/data again/debo
junk2
/oracle/foo
/db/foo
/db2/foo
/informix/debo/