What happens if the delimiter is indicated to be a null string (a string of zero characters)?

perl behaves inconsistently with regard to the "empty" regex:

my $string = 'Monk';
exit unless $string =~ /(o)/;

my @matches = $string =~ //;
warn join('=', @matches), "\n";

exit unless $string =~ /(o)/;

my @letters = split( //, $string );
warn join('-', @letters), "\n";
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