describe structure script (temp)

#!/usr/bin/perl
use strict;
use warnings;
use Scalar::Util qw(blessed reftype);

sub describe {
    my ($data, $indent) = @_;
    $indent //= 0;
    my $pad   = '  ' x $indent;
    my $class = blessed($data);
    my $r     = reftype($data) // '';

    return undef unless $r;

    if ($r eq 'HASH') {
        my (@scalars, @lines);
        for my $k (sort keys %$data) {
            my $d = describe($data->{$k}, $indent + 1);
            if (defined $d) {
                push @lines, "$pad  $k => $d";
            } else {
                push @scalars, $k;
            }
        }
        my $out = ($class ? "$class " : "") . "{\n";
        $out .= "$pad  " . join(", ", @scalars) . "\n" if @scalars;
        $out .= $_ for @lines;
        $out .= "$pad}\n";
        return $out;
    }
    elsif ($r eq 'ARRAY') {
        my @parts;
        for my $i (0 .. $#$data) {
            push @parts, describe($data->[$i], $indent + 1);
        }
        if (!grep { defined } @parts) {
            return ($class ? "$class " : "") . "[]\n";
        }
        my $out = ($class ? "$class " : "") . "[\n";
        for my $i (0 .. $#parts) {
            if (defined $parts[$i]) {
                $out .= "$pad  $parts[$i]";
            } else {
                $out .= "$pad  ,\n";
            }
        }
        $out .= "$pad]\n";
        return $out;
    }

    return undef;
}

print describe($const) // "(no structure)\n";