Copy year from filename



Since a few weeks I'm a enthusiastic user of mp3tag. It's a great tool to structure and optimize my mp3 database. By means of trial and error I'm using several actions. One I can't get to work is to copy a year which is mentioned in the title to the year field. String that I'm using is:
format value "YEAR": %_FILENAME%
Field: Year
Regexpr: ^(.+)\s(.+)\s(.+)\d+
Replace matches with: $3

Result is almost fine except that the number stated in the Year field resembles 3 # iso 4 e.g. 1949 = 194

Who can help me on the right string.