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

my @list = (7,15,2);
my @twoDmatrix =(); # the = () not really needed here.
                    # take off "my" if you want to "clear" the matrix
                    # later at some point, just: @twoDmatrix = ();
my $rows = @list;  # evaluation of @list in scalar context
                   # yields 3, the number of elements

# just replicated @list into multiple rows with
# simple offset to make each row different
# result is square matrix (num rows = num cols)

my ($row, $col);
for ($row=0; $row<$rows; $row++)
{
  for ($col=0; $col<@list; $col++)
  {
    $twoDmatrix[$row][$col] = $list[$col]+ $row+1; 
  }
}

print Dumper \@twoDmatrix;
print "element [1][2] is $twoDmatrix[1][2] \n";
print Dumper $twoDmatrix[1]; #twoDmatrix[1] is
                             #already a reference! no \ needed.

__END__
$VAR1 = [
          [
            8,
            16,
            3
          ],
          [
            9,
            17,
            4
          ],
          [
            10,
            18,
            5
          ]
        ];
element [1][2] is 4 
$VAR1 = [
          9,
          17,
          4
        ];