Match RAR archives
The Following can be used to find the first RAR file in a multi-volume archive. It will find *.part01.rar or *.rar depending on the naming convention in use.
.*[^p][^a][^r][^t]..\.rar$|.*part01\.rar$
If you need to find all the RAR files and SFV files (probably to delete them after extraction), the following will get them all.
.*\.r[0-9]{2}$|.*\.rar$|.*\.sfv$