That looks wrong to me, since therre is no need to constuct the $ra 100 times. Try it this way. Also try it with more patterns or do you search only for two?

...
my $t4 = new Benchmark;
my $ra = Regexp::Assemble->new();
$ra->add(@strings);
for (1..100) {
        while ( $sequence =~ /$ra/g) { my $val = pos($sequence) - 6; }
        }
[download]