I got a little lost in what you are trying to do. But looks like you are going to get a reference to an Array of Array. You don't want to "flatten" this out. It will be easier to process each row if you maintain this structure. See: http://perldoc.perl.org/5.8.8/perldsc.html#ARRAYS-OF-ARRAYS.

Here is some example code:

#!/usr/bin/perl 
use warnings;
use strict;
use Data::Dumper;

my @data = ([qw/one two three four five/],  #array of array
            [qw/ a   b    c    d     e/],);
            
my $dataref = \@data;

my @all;
push @all,@$dataref;  #not sure of need for this? but works.

print Dumper \@all;

print scalar @{$dataref->[0]},"\n"; #number of elements in row[0]
                                    # i.e. "5"
print $dataref->[0][1],"\n";        #prints "two", 2nd element of row 
+0

foreach my $element (@{$dataref->[0]}) #each element of row [0]
{
   print "$element ";
}
print "\n\n";

foreach my $row_ref (@all)  #deal with references to rows
{
   print "number of elements = ".scalar @$row_ref,"  @$row_ref\n";
   # of course number of elements will be the same in each row,
   #so only need to check for row[0] as above

}

__END__
$VAR1 = [
          [
            'one',
            'two',
            'three',
            'four',
            'five'
          ],
          [
            'a',
            'b',
            'c',
            'd',
            'e'
          ]
        ];
5
two
one two three four five 

number of elements = 5  one two three four five
number of elements = 5  a b c d e
[download]

To find "how many columns", check the number of elements that are in the row 0 of the data array.