This may be a poor workaround, but you could pad the input with '|you_know_what':

$ perl -le 'print for map "<$_>", split /,/, "a,b,c,,,,"'
<a>
<b>
<c>
$ perl -le 'print for map "<$_>", split /,/, "a,b,c,,,,FOO"'
<a>
<b>
<c>
<>
<>
<>
<FOO>
[download]

Update: now, of course inman's solution is a superior one and to all effects the right(TM) one, I'd say. I knew about this use of the LIMIT parameter, but for some reason it didn't spring to mind...