Given a source string of tags value pairs where the tags are represented by the character "A" and all text that is not "A" is considered to be the value associated with the tag.

The problem is to break up the source string into sub strings of TagValue.

So a source string of "A2ABA45" needs to be broken down to:

A2
AB
A45
[download]

Here's my first attempt:

@parts=split(/(A.+?)(?=A|$)/,"A2ABA45");
$i=1;
map {print $i++ . " -> $_\n"} @parts;
[download]

produces:

1 -> 
2 -> A2
3 -> 
4 -> AB
5 ->
6 -> A45
[download]

To get what I want I ended up with:

@parts=grep{$_}split(/(A.+?)(?=A|$)/,"A2ABA45");
$i=1;
map {print $i++ . " -> $_\n"} @parts;
[download]

which produces:

1 -> A2
2 -> AB
3 -> A45
[download]

The questions are:
1) why the undef entries are there to begin with?
2) is there a better way?

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