#!/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

##</code><code>##

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

my $file1=<<END;
#comment A
#comment B
#comment C

1 2 3
4 5 6
7 8 9
END

my $file2=<<END;
# just one comment
11 12 13
14 15 16
17 18 19
20 21 22
END

my @all_matricies;  # A 3-D structure;

foreach my $file_ref (\$file1, \$file2)
{
    open (my $fh_in, '<', $file_ref) or die "unable to open $!";

    my $matrix_ref = get_matrix($fh_in);
    push @all_matricies, $matrix_ref;
}

# In the 3-D structure, each element is a references 
# to a 2-D matrix.
# The scalar value of @all_matricies is the number of those
# 2-D matricies.

print "We have read a total of: ".@all_matricies." matricies:\n";

# Dump all the matricies that were read..

foreach my $matrix_ref (@all_matricies)
{
   print "\n"; 
   dump_matrix($matrix_ref);
}
print "\n";
print "Element[0,1,2]: $all_matricies[0][1][2]\n";
print "Element[1,2,1]: $all_matricies[1][2][1]\n";

print "\nNow transpose matrix #2:\n";
$all_matricies[1] = transpose_matrix ($all_matricies[1]);

# Dump all the matricies that were read..

foreach my $matrix_ref (@all_matricies)
{
   print "\n"; 
   dump_matrix($matrix_ref);
}


sub get_matrix  # reads a 2-D matrix from a file handle
{
    my $fileHandle = shift;
    my @matrix;
    
    while (defined (my $line =<$fileHandle>))
    {
        next unless $line =~ /^\s*\d/; # skip blanks or comments
        my @row = split ' ',$line;
        push @matrix, [@row];
    }

    return \@matrix;
}

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

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
   
   return \@result_matrix;
}


__END__
We have read a total of: 2 matricies:

1 2 3
4 5 6
7 8 9

11 12 13
14 15 16
17 18 19
20 21 22

Element[0,1,2]: 6
Element[1,2,1]: 18

Now transpose matrix #2:

1 2 3
4 5 6
7 8 9

11 14 17 20
12 15 18 21
13 16 19 22