my @motif = ( [30,43], [107,128], [209,254] );

# make sure it is in order by beginning position
@motif = sort { $a->[0] <=> $b->[0] } @motif;

my $last_group = 0;
for my $motif (@motif) {
    my $group = int(($motif->[0]+99)/100);
    if ($group != $last_group) {
        print "\n" if $last_group; # blank between groups
        print "group $group (", $group*100-99, "-", $group*100, "):\n";
        $last_group = $group;
    }
    print "> genome.ptt_", $motif->[0], " ", $motif->[1], "\n",
        substr($string, $motif->[0]-1, $motif->[1] - $motif->[0]), "\n";
}