my @list = "A".."C"; my @tojoin = "W".."Z"; ITEM: for (my $i = 0; $i <= $#list; $i++) { for (map "$list[$i]$_", @tojoin) { push @list,$_; last ITEM if /^AYW$/; } } use Data::Dumper; print Dumper \@list; #### @hash{@list} = (1) x @list; $hash{$_} = 1 for @list;