[ ... ] means "Construct an array with '...' as content, and return a reference to it." This is documented in perlref.

$-[0] and $+[0] are elements of the special arrays @- and @+. Refer to perlvar for more information.

In reply to Re^4: 'grouping' substrings? by ikegami
in thread 'grouping' substrings? by Anonymous Monk

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