Hi

I simplified the code, and replaced tr/()/<>/ to make it more readable: 

$_='a<b<c<d><e>>f>g<h><<i>j>';
 
$re = qr{
          <                # anchor at first paren as  wanted
          (                # paren group 1 
            (?:
              (?> [^<>]+)  # Non-parens without backtracking
            |
              <
              (?1)         # Recurse to start of paren group 1
              >
            )*
          )
      }x;
 
/$re/;
print $1;

[download]
perl /tmp/tst2.pl
b<c<d><e>>f

[download]

Cheers Rolf

In reply to Re^2: Eternal question of parsing parentheses by LanX
in thread Eternal question of parsing parentheses by Anonymous Monk

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