If you add capturing you can see what it's doing .. 
    my $didit=/^
        a         # literal a
        \s*       # optional whitespace
        ((?:
            $re
            \s*
        )+)
        (.*)        # something
        42        # literal 42
    $/x;
    print Dumper [$_, $didit?($1,$2):(undef,undef),  $didit];

[download]
For exampl, with #2 & #6 that gives: 
# 2
$VAR1 = [
          'a [foo]  [bar]bla[quux] grmbl42',
          '[foo]  [bar]',
          'bla[quux] grmbl',
          '1'
        ];
# 6
$VAR1 = [
          'a [fo]o] grmbl42',
          '[fo]',
          'o] grmbl',
          '1'
        ];

[download]
The issue is with the "something" .* -- it just sucks up anything bad.

In reply to Re: Regexp::Common balanced brackets non-capture multiple occurances by davidrw
in thread Regexp::Common balanced brackets non-capture multiple occurances by Anonymous Monk

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