# called as insert1( \@ary, 1, $_ ) for $START .. $END
sub insert1 {
  my ( $ra, $index, $elem ) = @_;
  @$ra = @$ra[0 .. $index-1], $elem, @$ra[$index .. @$ra-1];
}
# I tested with 
sub insert1 {
  my ( $ra, $elem, $index ) = @_;
  @$ra = @$ra[0 .. $index-1], $elem, @$ra[$index .. @$ra-1];
}
# called as insert1( \@ary, 1, $_ ) for $START .. $END