Hey! You can't see the join's :)

#! perl -sw
use strict;
sub npAndAList{$"=', '; return unless @_; @_==1 and "@_" or "@_[0 .. $
+#_-1] and $_[-1]" }
print npAndAList(qw(a b c d e)[0..$_]),$/ for -1..4;
__DATA__
a
a and b
a, b and c
a, b, c and d
a, b, c, d and e
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