$ cat melt.tsv
Month    Zone    Replicate    variable    value
Sept    1    1    SpeciesA    5
Sept    1    1    SpeciesB    10
Sept    1    1    SpeciesC    15
Sept    1    2    SpeciesA    0
Sept    1    2    SpeciesB    5
Sept    1    2    SpeciesC    10
Sept    1    3    SpeciesA    5
Sept    1    3    SpeciesB    0
Sept    1    3    SpeciesC    5
Sept    2    1    SpeciesA    5
Sept    2    1    SpeciesB    5
Sept    2    1    SpeciesC    5
Sept    2    2    SpeciesA    10
Sept    2    2    SpeciesB    15
Sept    2    2    SpeciesC    10
Sept    2    3    SpeciesA    0
Sept    2    3    SpeciesB    0
Sept    2    3    SpeciesC    5

$ cat melt.pl
#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd /;
use DBI;
use DBD::CSV;
my $dbh = DBI->connect(
    "dbi:CSV:",
    undef, undef,
    { RaiseError => 1 },
);
$dbh->{csv_tables}{melt} = {
    eol         => "\n",
    sep_char    => "\t",
    quote_char  => undef,
    escape_char => undef,
    file        => 'melt.tsv',
    col_names   => [qw( Month    Zone    Replicate    Species Specnum 
+)],
};


my $names = $dbh->selectall_arrayref('SELECT DISTINCT species FROM mel
+t');
dd( $names );
dd( shotsky => $dbh->selectall_arrayref(q{ select * from melt where Sp
+ecies = ?}, { Slice => {} }, 'SpeciesB' ) );
for my $name ( @$names ){
    dd( 
    $name => $dbh->selectall_arrayref('
select
    Month,
    Zone,
    Species,
    AVG(Specnum) MEAN
FROM
    melt
WHERE
    melt.Species = ?
                ',
            { Slice => {} },
            $name,
        )
    );
}

__END__
[["variable"], ["SpeciesA"], ["SpeciesB"], ["SpeciesC"]]
(
  "shotsky",
  [
    {
      month     => "Sept",
      replicate => 1,
      species   => "SpeciesB",
      specnum   => 10,
      zone      => 1,
    },
    { month => "Sept", replicate => 2, species => "SpeciesB", specnum 
+=> 5, zone => 1 },
    { month => "Sept", replicate => 3, species => "SpeciesB", specnum 
+=> 0, zone => 1 },
    { month => "Sept", replicate => 1, species => "SpeciesB", specnum 
+=> 5, zone => 2 },
    {
      month     => "Sept",
      replicate => 2,
      species   => "SpeciesB",
      specnum   => 15,
      zone      => 2,
    },
    { month => "Sept", replicate => 3, species => "SpeciesB", specnum 
+=> 0, zone => 2 },
  ],
)
(
  ["variable"],
  [
    { MEAN => undef, Month => undef, Species => undef, Zone => undef }
+,
  ],
)
(
  ["SpeciesA"],
  [
    { MEAN => undef, Month => undef, Species => undef, Zone => undef }
+,
  ],
)
(
  ["SpeciesB"],
  [
    { MEAN => undef, Month => undef, Species => undef, Zone => undef }
+,
  ],
)
(
  ["SpeciesC"],
  [
    { MEAN => undef, Month => undef, Species => undef, Zone => undef }
+,
  ],
)
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