my $csv = Text::CSV_XS->new ({ binary => 1 });
open my $dta, "<", "data.csv" or die "data: $!\n";
my @rows;
while (my $row = $csv->getline ($dta)) {
    push @rows, $row;
    }
$csv->eof or $csv->error_diag;
close $dta;

# pivot
my @data = map { my $col = $_; join "|", map { $_->[$col] } @rows } 0..$#{$rows[0]};


##</code><code>##

123,foo,2,FOO
234,bar,2,BAR
345,zap,3,ZAP
456,bok,5,BOK

##</code><code>##

(   "123|234|345|456",
    "foo|bar|zap|bok",
    "2|2|3|5",
    "FOO|BAR|ZAP|BOK")