Oops, I read that too late ... > Let's say my original lines are: > CN=DATA.OU=XYZ.O=CO > CN=DATA.OU=XYY.OU=MEM.O=CO > CN=DATA.OU=XZZ.OU=OOP.O=CO > > I want them to look like: > CN=XYZ_DATA.OU=XYZ.O=CO > CN=XYY_DATA.OU=XYY.OU=MEM.O=CO > CN=XZZ_DATA.OU=XZZ.OU=OOP.O=CO then the perl script would be perl -pne 's/(CN=)(DATA\.OU=)((.*?)\.O.*)$/$1$4_$2$3/' /file/name Best regards, Peter.