while (<$in_file>) {
    chomp;
    if (/^SAMPLE/) {
        my ( $placeholder, @coords ) = split /,/;
        foreach my $coord (@coords) {
            push @snp_bins, int( $coord / 100_000 );
        }
    }
    else {
        my ( $id, @snps ) = split /,/;
#need to check here that $#snps == $#snp_bins ?
        foreach my $index ( 0 .. $#snp_bins ) {
          push( @{ $data{$id}[ $snp_bins[$index] ] }, $snps[$index] );
        }
    }
}