for (@arr1) {  #for each element in @arr1
    s/\s+$//;  #replace one or more spaces at the end of it
               #with nothing (deleting them)
}

##</code><code>##

for (@arr1) {
    while ( substr($_,-1,1) eq ' ' ) {  # while the last char is space
       chop();                          # remove the last char
    }
}

##</code><code>##

for (@arr1) { chop() while substr($_,-1,1) eq ' ' }