<form action="b1.pl" method="GET">
   <p><input type="submit" value="Отправить"></p>
   <p><input type="checkbox" name="a[]" value="1417"> 1417</p>
   <p><input type="checkbox" name="a[]" value="1680"> 1680</p>
   <p><input type="checkbox" name="a[]" value="2312"> 2312</p>
   <p><input type="checkbox" name="a[]" value="1521"> 1521</p>
  </form>

...
use CGI qw/:standard/;
use CGI::Carp 'fatalsToBrowser';
use Data::Dumper;
our $q = new CGI;
print "Content-Type: text/html\n\n";
$del = $q->param('a');
print Dumper($del);
...