There is no Arabic firmware, but I have made Arabic language support pack for Pearl. Allows input and changes OS language to Arabic:
1. Download zSHARE - pearl_arabic.zip
2. Connect BlackBerry to PC with USB (must have microSD card installed)
3. Extract pearl_arabic.zip to microSD in your BlackBerry.
4. Disconnect from PC.
5. In BlackBerry open Media, press BlackBerry button, choose Explore.
6. Find the file arabic.jad on your microSD. Press to open it.
7. Download. When finished, battery pull.
8. ENJOY.
