I think you can do this directly in DBD::CSV with a combination of joins, user-defined functions, and the new CREATE TABLE AS SELECT ... syntax. The last two features require the SQL::Statement 1.14 or later.

Here's an example of a simple calculation with a User Defined Function

#!/usr/bin/perl -w
use strict;
use DBI;
my $dbh=DBI->connect("dbi:CSV(RaiseError=1):csv_eol=\n");

sub MyCalc { $_[3] * 2 }
$dbh->do("CREATE FUNCTION MyCalc");

my $sth = $dbh->prepare(q{  SELECT sales,MyCalc(sales) FROM Test });
$sth->execute;
$sth->dump_results();
__END__
#
# given sales values of 2 and 5, this script outputs
#
#    2,4
#    5,10
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See SQL::Statement::Functions for more on creating User Defined Functions.

To create a new table from a join of two existing tables, use something like:

CREATE TABLE new AS SELECT $cols FROM old1 JOIN old2 WHERE ...