sub WEED {
    my( $span, %matches) = @_;
    my %sets;
    my @newfast;

    for my $fasta_id ( @fastheaders ) {
        my $setscounter = 0;
        next unless defined %{ $matches{ $fasta_id } };
        print "Currently analysing results from sequence:\n     $fasta_id\n";
        my @sortedKeys = sort { $a <=> $b } keys %{ $matches{ $fasta_id } };

        for my $site ( @sortedKeys ) {
            last unless @{ $matches{ $fasta_id }{ $site } };

            WEEDLOW: for my $low ( @{ $matches{ $fasta_id }{ $site } } ) {
                my $lowerlimit = $low + 0;
                my $upperlimit = $span + $lowerlimit;

                for my $sitekey (  @sortedKeys ) {
                    next unless defined @{ $matches{ $fasta_id }{ $sitekey } };
                    @{ $sets{ $fasta_id }[ $setscounter ]{ $sitekey } } = grep {
                        $_ >= $lowerlimit and $_ <= $upperlimit
                    } @{ $matches{ $fasta_id }{ $sitekey } }

                    unless( @{ $sets{ $fasta_id }[ $setscounter ]{ $sitekey } } ) {
                        undef $sets{ $fasta_id }[ $setscounter ] };
                        next WEEDLOW;
                    }
                }
                for my $checkhash ( keys %{ $sets{ $fasta_id }[ $setscounter ] } ) {
                    unless( defined $sets{ $fasta_id }[ $setscounter ]{ $checkhash }[ 0 ] ) {
                        undef $sets{ $fasta_id }[ $setscounter ] };
                        last;
                    }
                }
                if( scalar keys %{ $sets{ $fasta_id }[ $setscounter ] } < $num ) {
                    undef $sets{ $fasta_id }[ $setscounter ];
                }
                $setscounter++ if scalar %{ $sets{ $fasta_id }[ $setscounter ] };
            }
        }
        if( @{ $sets{ $fasta_id } } ) {
            pop @{ $sets{ $fasta_id } } unless scalar %{ $sets{ $fasta_id }[ $#{ $sets{ $fasta_id } } ] };
        }
        if( @{ $sets{ $fasta_id } } ) {
            push @newfast, $h;
        }
        else {
            delete $sets{ $fasta_id };
        }
    }
    @fastarray = @newfast;
    return %sets;
}