if (index($data,$id)+1){

##</code><code>##

Benchmark: timing 10000 iterations of index, regex...
     index:  3 wallclock secs ( 3.52 usr +  0.00 sys =  3.52 CPU) @ 2840.91/s (n=10000)
     regex: 92 wallclock secs (91.44 usr +  0.00 sys = 91.44 CPU) @ 109.36/s (n=10000)

##</code><code>##

sub regex {
    foreach my $data (@db) {
        foreach my $id (@id) {
            if ($data =~ /$id/) {1}
        }
    }
}

sub index {
    foreach my $data (@db) {
        foreach my $id (@id) {
            if (index($data,$id)+1) {1}
        }
    }
}