I can see in the bitcointools 's python code that database are DB_BTREE, so I tried:
use DB_File;
my $db = tie my %h, 'DB_File', ".bitcoin/blockindex.dat", O_RDONLY, 0644, $DB_BTREE;
END { undef $db, untie %h if defined $db }
printf "%s: %d\n", $_, length($_) for keys %h;
but this gives me only one line:
main: 4
What am I missing? I can understand the the data is a bit serialized or something but I had expexted to have at least a bigger entry.