may I push it as far as to dare to say that it is a bug?

well, probably not, as it is well documented on perlfunc

A workaround is to set the limit explicetly to undef (though, it generates a warning):

$count = () = split ' ', $_, undef;
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amazingly, setting it to 0 doesn't work:

$ perl -MO=Deparse -e '$a = () = split(" ", $_, undef)'
$a = () = split(" ", $_, undef);

$ perl -MO=Deparse -e '$a = () = split(" ", $_, 0)'
$a = () = split(" ", $_, 1);
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A better workaround that doesn't generate warnings is to use a zero-but-true value:

$count = () = split ' ', $_, '0e0';
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that is parsed as:

$ perl -MO=Deparse -e '$a = () = split(" ", $_, "0e0")'
$a = () = split(" ", $_, '0e0');
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