#!/usr/bin/perl -l

$dialog->{attributes}{control1} = "abc";
$dialog->{attributes}{control2}[0] = "cde";
$dialog->{attributes}{control2}[1] = "fgh";

for my $control (keys %{ $dialog->{attributes} }) {

    if (ref $dialog->{attributes}{$control} eq 'ARRAY') {
        print "@{ $dialog->{attributes}{$control} }";
    } else {
        print $dialog->{attributes}{$control};
    }
}

__END__
abc
cde fgh
[download]

Or, with an intermediate variable (better readable IMHO):

for my $control (keys %{ $dialog->{attributes} }) {

    my $val = $dialog->{attributes}{$control};
    
    if (ref $val eq 'ARRAY') {
        print "@$val";
    } else {
        print $val;
    }
}
[download]

And in case there could also be other types (such as hashrefs), you should either test for them, too, or at least write

    ...
    } elsif (!ref $val) {
        print $val;
    }
[download]

for the simple scalar values.