Problems with Search in 2.5.1

[Jan-Michael]

Via Sventon I access a svn which contains documents (pdfs, docs, etc). I tested the search function in 2.1.6 and found that it is pretty usable for searching the svn for certain documents. Then I installed 2.5.1 and saw that the search seems to work completely differently and, in case of my usage, not understandable and usable.

Example:
the documents follow the syntax: <Module>_<document type>_<language>_<version>.<extension>, e.g. ABModul_User_ger_9.1-1.pdf

2.1.6:
Search for "ger*pdf": all german pdf-documents
Search for "ger*9*pdf: all german pdf-documents of version 9
any combinations produce an understandable result

2.5.1:
Search for "pdf": all pdf files
Search for "user_ger" or "user*ger": all german user-documents
Search for "user_ger_9: no result
Search for "user*ger*9": all german user-documents of version 9
Search for "ger*9*pdf" or "9*pdf": no result
Search for "user*pdf": no result
Search for "modul" or "*modul": no documents (just single directories with the exact name)

Does anybody know, whether there is any description how the search is exactly working in 2.5.1 (I didn't find a description in the Wiki) or can explain the above result?
Is there any way to restore the previous search behaviour?

Jan-Michael