Data Dumper is *everyone's* friend (though you'd want to make sure that the default output for your version is the same as for mine):

use Data::Dumper;

sub tell_structure {
    (my $string = Dumper(shift)) =~ s/\$VAR1 = //;
    
    my %regexes = (
        qr/^\[\s*/ => 'array',
        qr/^\{\s*'\w*' => / => 'hash',
        qr/^'\w*',*\n/ => 'value',
    );
    my @result;
    my $regex = join "|", keys %regexes;
    
    OUTER: while ($string =~ /$regex/) {
        for my $regex (keys %regexes) {
            if ($string =~ s/$regex//s) {
                last OUTER if $regexes{$regex} eq 'value';
                push @result, $regexes{$regex};
                last;
            }
        }
    }
    return @result;
}
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Then you can compare the contents of two returned arrays to determine whether the structures referenced are the same. Or you cd use this to tell you what you've got:

sub print_results {
    if (@_ == 0) {
        print "This data structure is a scalar";
    }
    else {
        if ($_[0] eq 'array') {
            print "This data structure is an array";
        }
        else {
            print "This data structure is a hash";
        }
        shift;
        for (@_) {
            if ($_ eq 'hash') {
                print ' of hashes';
            }
            elsif ($_ eq 'array') {
                print ' of arrays';
            }
        }
    }
    print "!\n";
}
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§ George Sherston