use Perl6::Form;
sub hashes {
my ($match,$opts) = @_;
$opts->{lfill}='>> ';
$opts->{rfill}='<< ';
return '{I{'.length($match).'}I}';
}
print form
{field=>[qr/(#+)/=>\&hashes]},
"[###|###############################]",
[1,2,3], [qw[First Second Last]];