remove suffix from a wavename

Hi I am trying to make new waves the names of which come from my old wave names. I want to remove the suffix of the old name waves and add on a new suffix because my old wave names are too long and if I only add on another suffix igor would report an error. Since my old wave names are not of equal length or have a pattern, I found it hard to use string indexing with wavename[x,x] to extract the characters. I wonder since strings can be combined by a "+", if there is a way to "-" the characters then? Thank you very much!