Pentominous

Description
Pentominous is a region division puzzle where the grid must be divided into pentominoes.

Rules
The objective is to divide the grid into pentominoes, subject to the following rules:


 * 1) No two congruent pentominoes, including rotations and reflections, are allowed to share an edge.
 * 2) Letters indicate which pentomino occupies that cell; pentominoes may contain any number of letters (including zero).

Example
A standard 10x10 Pentominous and its solution.

Variants
Unless otherwise indicated, standard pentominous rules apply to all variants.

Pearl Pentominous: Every pentomino must contain one pearl.

Pentominous Borders: Some borders between pentominoes are given.