The block can change depending on the page being viewed.

2 uses of BLOCK_CACHE_PER_PAGE
hook_block in developer/hooks/core.php
Declare a block or set of blocks.
profile_block in modules/profile/profile.module
Implementation of hook_block().

File

modules/block/block.module, line 56
Controls the boxes that are displayed around the main content.

Code

define('BLOCK_CACHE_PER_PAGE', 0x4);