> # But why doesn't this work?
> my $foo = () = split /,/, $bar;
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Because split is DWIM-happy (or DWYTIM -- Do What You Think I Mean), and it's told the length of the array it is assigning into so it can stop looking after it fills your array.

my $foo = () = split(/,/, $bar, -1) almost works, but it doesn't strip trailing undefs like it would in list context without the third param (try it with "a,b,,").

If you don't mind wiping out @_, then just be explicit about it:

my $foo = @_ = split /,/, $bar