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

my @matrix;

while (defined (my $line=<DATA>))
{
   next unless $line =~ /^\s*\d/; # skip blanks or comments
   my @row = split ' ',$line;
   push @matrix, [@row];
}

print "input matrix:\n";
dump_matrix(\@matrix);

my $transposed_ref = transpose_matrix (\@matrix);

print "\ntransposed matrix:\n";
dump_matrix($transposed_ref);

# a "ragged" matrix would have differing number of
# elements in each row. This won't work for that.

sub transpose_matrix   # only for "non-ragged" matricies
{
   my $AoAref = shift;
   my @input_matrix = @$AoAref; #local copy to destroy
   my @result_matrix;
      
   while (defined $input_matrix[0][0])
   {
      my @new_row;
      foreach my $row_ref (@input_matrix)
      {
         push @new_row, (shift @$row_ref);
      }
      push @result_matrix, [@new_row];  
   }
   # at this point, @input_matrix is an array of references
   # to empty rows, rows still "exist" but have no data in them
   
   print "At end of transpose, local copy of input_matrix is like this:\n";
   print Dumper \@input_matrix;
   
   return \@result_matrix;
}

sub dump_matrix
{
   my $AoAref = shift;
   
   foreach my $row_ref (@$AoAref)
   {
      print "@$row_ref\n";
   }
}

=Prints
input matrix:
1 2 3
4 5 6
7 8 9
At end of transpose, local copy of input_matrix is like this:
$VAR1 = [
          [],
          [],
          []
        ];

transposed matrix:
1 4 7
2 5 8
3 6 9
=cut



__DATA__
#title line - (skipped it with $nextUnless)
#title line - (skipped it with $nextUnless)
1 2 3
4 5 6
7 8 9