print Dumper($q->param('at0'))."\n"; # generates:
$VAR1 = 'H&C05.01';
$VAR2 = 'SETT04.03';

##</code><code>##

print Dumper([$q->param('at0')])."\n"; # generates:
$VAR1 = [
          'H&C05.01',
          'SETT04.03'
        ];

##</code><code>##

print \@{$q->param('at0')}."\n"; # generates:
Can't use string ("H&C05.01") as an ARRAY ref while "strict refs" in use at ...