Hi! I am trying to match C++ templates: 
#!/usr/bin/perl

$cparens = qr/
(?<intern>
 \<
 (?:
  [^<>]++
  |
  (?$+{intern})
 )*+
 \>
)
/x;

$ks="BinaryNode<OpAdd1<OpAdd2>,OpMulAdd2<OpMulAdd>>";

if ($ks =~ m/
([^<>]++)
    \<(?'part1'[^<>]++(?:$cparens)?)
    \,(?'part2'[^<>]++(?:$cparens)?)
    \>
    /x) {
  print "ok\n";
}

print "p1 $+{part1}\n";
print "p2 $+{part2}\n";

[download]

This matches as supposed and prints the part1 and part2 of the toplevel template:

p1 OpAdd1<OpAdd2>

p2 OpMulAdd2<OpMulAdd>

But, when I add one more level of recursion, like adding to one of the parts: 

$ks="BinaryNode<OpAdd1<OpAdd2<a>>,OpMulAdd2<OpMulAdd>>";

[download]

p1

p2

it doesn't match anymore!

I don't follow this logic. Does anybody know why this behaviour is shown?

Frank

In reply to recursive pattern by Anonymous Monk

Title:
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