use unshift for Prepends list to the front of the array.

use strict;
use Data::Dumper;
my $form = {};
$form->{days} = [
          '2011-02-26',
          '2011-02-25',
          '2011-02-24',
          '2011-02-23',
          '2011-02-22',
          '2011-02-21',
          '2011-02-20',
        ];
my @extra_date = ('2011-03-01','2011-02-28','2011-02-27');
unshift(@{$form->{days}}, @extra_date);
print Dumper($form->{days});
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Output:

$VAR1 = [
          '2011-03-01',
          '2011-02-28',
          '2011-02-27',
          '2011-02-26',
          '2011-02-25',
          '2011-02-24',
          '2011-02-23',
          '2011-02-22',
          '2011-02-21',
          '2011-02-20'
        ];
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