In this context (&Dumper(@somearray);) & is not required and is normally not used.

Note too that Dumper(\@somearray); generally gets you better output. (see sample below).

Note that your sample code doesn't actually demonstrate a problem. duff has given an answer that probably answers your question, but not by carefull examination of your sample code or its output. In general something like the following will get you better answers sooner:

use strict;
use warnings;
use Data::Dumper;

my @somearray = (['1', 2], ['3', 4]);

print "Unreffed:\n" . Dumper (@somearray) . "\n";
print "Reffed:\n" . Dumper (\@somearray) . "\n";

push @somearray, (['5', 6], ['7', 8]);
print Dumper (\@somearray) . "\n";

@somearray = (['9', 10], ['11', 12]);
print Dumper (\@somearray) . "\n";
[download]

Prints:

Unreffed:
$VAR1 = [
          '1',
          2
        ];
$VAR2 = [
          '3',
          4
        ];

Reffed:
$VAR1 = [
          [
            '1',
            2
          ],
          [
            '3',
            4
          ]
        ];

$VAR1 = [
          [
            '1',
            2
          ],
          [
            '3',
            4
          ],
          [
            '5',
            6
          ],
          [
            '7',
            8
          ]
        ];

$VAR1 = [
          [
            '9',
            10
          ],
          [
            '11',
            12
          ]
        ];
[download]