$package
$desc
 \$tree = $package\>new$new_trailing
 \$tree = $long$func_trailing
 \$tree = $short$func_trailing

Creat a new empty tree.
 \$tree>insert$key_value_arg
 \$tree>insert_after$key_value_arg

Insert an entry into the tree. If there are any entries with the same key size, insert the new one after them.
 \$tree>insert_before$key_value_arg

Insert an entry into the tree. If there are any entries with the same key size, insert the new one before them.
 \$tree>delete(\$key)
 \$tree>delete_last(\$key)

Delete one entry whose key is equal to \$key. If there ary more than one entry with the same key size, delete the last inserted one.
 \$tree>delete_first(\$key)

Delete one entry whose key is equal to \$key. If there ary more than one entry with the same key size, delete the first inserted one.
 \$size = \$tree>size

Get the number of entries in the tree
 $key_value_ret = \$tree>find(\$key, \$limit=1)
 $key_value_ret = \$tree>find_first(\$key, \$limit=1)

Get entries with key sizes equal to \$key, from the first inserted one to the last inserted one.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \$tree>find_last(\$key, \$limit=1)

Get entries with key sizes equal to \$key, from the last inserted one to the first inserted one.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \$tree>find_lt(\$key, \$limit=1)

Get entries, whose keys are smaller than \$key, from the largest entry.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \$tree>find_le(\$key, \$limit=1)

Get entries, whose keys are smaller than or equal to \$key, from the largest entry.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \$tree>find_gt(\$key, \$limit=1)

Get entries, whose keys are greater than \$key, from the smallest one.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \$tree>find_ge(\$key, \$limit=1)

Get entries, whose keys are greater than or equal to \$key, from the smallest one.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \$tree>find_gt_lt(\$lower_key, \$upper_key)

Get entries, whose keys are greater than \$lower_key and smaller than \$upper_key, from the smallest one to the largest one.
 $key_value_ret = \$tree>find_gt_le(\$lower_key, \$upper_key)

Get entries, whose keys are greater than \$lower_key and smaller than or equal to \$upper_key, from the smallest one to the largest one.
 $key_value_ret = \$tree>find_ge_lt(\$lower_key, \$upper_key)

Get entries, whose keys are greater than or equal to \$lower_key and smaller than \$upper_key, from the smallest one to the largest one.
 $key_value_ret = \$tree>find_ge_le(\$lower_key, \$upper_key)

Get entries, whose keys are greater than or equal to \$lower_key and smaller than or equal to \$upper_key, from the smallest one to the largest one.
 $key_value_ret = \$tree>find_min(\$limit=1)

Get entries from the one with smallest key. If there are more than one entries with smallest key, begin from the first inserted one.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \$tree>find_max(\$limit=1)

Get entries from the one with largest key. If there are more than one entries with smallest key, begin from the last inserted one.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \&tree>skip_l(\$offset, \$limit=1)

Get the first entry from one with the smallest key after skipping \$offset entries.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 $key_value_ret = \&tree>skip_g(\$offset, \$limit=1)

Get the first entry from one with the largest key after skipping \$offset entries.
The optional \$limit (default 1) indicates the maximum entry number you will get, \$limit=1 means unlimited.
 \$count = \$tree>count_lt(\$key)

Get the number of entries whose keys are smaller than \$key.
 \$count = \$tree>count_le(\$key)

Get the number of entries whose keys are smaller than or equal to \$key.
 \$count = \$tree>count_gt(\$key)

Get the number of entries whose keys are greater than \$key.
 \$count = \$tree>count_ge(\$key)

Get the number of entries whose keys are greater than or equal to \$key.
 \$dump_str = \$tree>dump

Get a string which represent the whole tree structure. For debug use.
 (\$order_consistent, \$size_consistent, \$balanced) = \$tree>check

Check the tree property. For debug use.
 \$ever_height = \$tree>ever_height

Get the maximum height the tree has ever been. For debug use