Re: mysteries of regex substring matching

[LanX]

> So, is there a way to use capture groups to match multiple times like separate groups does in the first example?

It depends what your goal is.

If it's simply using a quantifier {4} the answer is no, because only the last match will be kept for the unique first group , that's why you get 01D9 at the end. Not a mystery.

But there are numerous workarounds I can think of.

Like

• using the /g modifier in a loop /(....)/g
• reading the last capture with embedded Perl code like /(....(?{print $1})){4}/

updates

• minor corrections
• links to perlretut

[LanX]

> using the /g modifier in a loop /(....)/g

demo:

  DB<53> $x = q[AAD34017837201D98AAED18778DEF993];

  DB<54> $x =~ m/(....)/g and say $1 for 1..4
AAD3
4017
8372
01D9

  DB<55>

[LanX]

> reading the last capture with embedded Perl code like /(....(?{print $1})){4}/

demo: (using /x for clarification)

  DB<66> $x = q[AAD34017837201D98AAED18778DEF993];

  DB<67> $x =~ m/(?: (....) (?{say $1}) ) {4} /x
AAD3
4017
8372
01D9

  DB<68>

update

I think this explains your "mystery", they all match but only the last one is kept in $1.