&Chg_User ($other_user);
&Chg_Directory ($dir_location);
…
…
…
## the sub_routines below
sub Chg_User {
   my @chg_args = ("su”,  “$_[0]");
   my $chg_result = system(@chg_args);   # updates to user but returns to the UNIX command prompt
   print ("cOmMaNd LiNe \n");	  #never gets here unless I type “exit” at the UNIX command prompt
        if ( $chg_result == -1) {
                print "wrong password: $!\n";
               exit (-1);
        }
}
sub Chg_Directory {
   system (“cd”, “$_[0]”);
}