An interesting observation. The behaviour for (?:...) and naked match strings is however appropriate provided you have at least one capture (...) in the RE.

@ary = 'stuff stuff stuff' =~ m/(?:st)u(ff)/g;
print "@ary";
__DATA__
ff ff ff
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Depending on your viewpoint your observation represents a bug or a feature!

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print