if (-t STDIN) { 
   # output prompt
}

##</code><code>##

my $old_handle;
if (-t STDOUT) { 
   open (MORE, "| more") or die "No more $!\n";
   $old_handle = select MORE;
}

##</code><code>##

END {
   if (defined $old_handle) {
      select $old_handle;
      close MORE;
   }
}