The mistake/typo in regex used in LLD rule may cause deleting of configuration/history/events for many hosts. For example, incorrect "File systems for discovery" regular expression may cause of deleting thousands of items/triggers and history/events.

It would be great to improve our documentation:
1. add "important" note about this after the table with filter description (https://www.zabbix.com/documentation/2.4/manual/discovery/low_level_discovery#discovery_of_file_systems)
2. add several additional, more complex examples in "Regular expressions" (https://www.zabbix.com/documentation/2.4/manual/regular_expressions):

• what logical operator Zabbix uses if there are several sub expressions. OR? AND? e.g.:

  1	»	^(database,name=report)	[Result is TRUE]
  2	»	^(database,name=zabbix)	[Result is TRUE]
  3	»	^(database,name=report1)$	[Result is FALSE]

  Will "database,name=report11" pass it?

• what about this one:

  1	»	^(database,name=zabbix|database,name=report)	[Result is TRUE]
  2	»	^(database,name=report1)$	[Result is FALSE]

  ?

• some example with "?" or "*" metacharacters:

  1	»	^(database,name=zabbix)	[Result is TRUE]
  2	»	^(database,name=repor.*)	[Result is FALSE]

etc
3. Add "Combined result" description to improve "Test" tab documentation (https://www.zabbix.com/documentation/2.4/manual/regular_expressions). What does FALSE mean?