$def =~ s/
    (^\.\w+\s)      ## $1 := A '.', followed a word and a space
    (\w+)           ## $2 := Another word
    (\s+)           ## $3 := some whitespace
    (.+)            ## $4 := Some anything
    (               ## $5
        ^           ## The start of string/line
        select      ## The word 'select'
        \.          ## A literal '.'
        .           ## Any single character
        $           ## The end of the line/string
    )
/$2$5/x;        ## put back just first word and the 'select' etc