use strict;
use warnings;
use 5.012;

use DBD::CSV;

my $dbh =
  DBI->connect( "dbi:CSV:f_dir=.", undef, undef,
    { FetchHashKeyName => "NAME_lc", RaiseError => 1, PrintError => 1, } )
  or die $DBI::errstr;

my $query =
'SELECT key1, key2, data1, data2, data3, data4, data5 FROM file1 JOIN file2 WHERE file1.key1 = file2.key1 AND file1.key2 = file2.key2';
my $sth = $dbh->prepare($query);
$sth->execute();
while ( my @row = $sth->fetchrow_array ) {
    say join '|', @row;
}
$sth->finish();