Then why not use DBD::CSV directly?

$ cat test.csv
3211111,100,3.2
3211112,101,3.2
3211111,100,1.2
3211112,100,2.2
3211113,100,5.2
3211112,100,0.3

$ cat test.pl
use 5.18.2;
use warnings;

use DBI;
use Text::CSV_XS qw(csv);
my $dbh = DBI->connect ("dbi:CSV:");
   $dbh->{csv_tables}{sampleData} = {
    file      => "test.csv",
    col_names => [qw( sample input amount )],
    };

csv (in => $dbh->selectall_arrayref ("
    SELECT sample, input, SUM (amount)
      FROM sampleData
  GROUP BY sample, input
  ORDER BY sample, input"));

$ perl test.pl
3211111,100,4.4
3211112,100,2.5
3211112,101,3.2
3211113,100,5.2
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