use strict;
my @transpose;  # this will be an array of arrays
my $ncols = 0;

while (<>)
{
    chomp;
    my @cols = split(/,/);
    if ( $ncols ) {
        die "Line $. doesn't have $ncols columns\n"
            if ( $ncols != scalar @cols );
    } else {
        $ncols = scalar @cols;
    }
    foreach my $i (0..$#cols) {
        push( @{$transpose[$i]}, $cols[$i] );
    }
}
my $nrows = $.;
for (0..$ncols-1) 
{
    &fisher_yates_shuffle( $transpose[$_] );
}

foreach my $i (0..$nrows-1) {
    my @cols = ();
    foreach my $j (0..$ncols-1) {
        push( @cols, $transpose[$j][$i] );
    }
    print join( ",", @cols ) . "\n";
}