#!perl -w
use strict;
use Text::CSV_XS;
use IO::File;
my $csv   = Text::CSV_XS->new( {binary=>1} );
my $fh    = IO::File->new('myfile.csv');
my $count = 0;
while (my $cols = $csv->getline($fh)) {
    last unless @$cols;
    print ++$count . ". @$cols\n";
}
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update Or, to create your file #3 from files #1 and #2, I'd do:

#!perl -w
use strict;
use DBI;
my $dbh=DBI->connect("dbi:CSV(RaiseError=1):csv_eol=\n");
$dbh->{csv_tables}->{tbl1}->{file}='tmp.csv';
$dbh->{csv_tables}->{tbl2}->{file}='tmp2.csv';
$dbh->{csv_tables}->{tbl3}->{file}='combined.csv';
$dbh->do("CREATE TABLE tbl3 AS SELECT * FROM tbl1 NATURAL JOIN tbl2");
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