>perl -wMstrict -le
"my $x;
 sub Sbr { $x = 1 + scalar @_;  return    }
 sub Sel { $x = 1 + scalar @_;  return () }
 my ($s, @ra);
 $s = Sbr();
 print 'scalar bare return ', defined $s ? '' : 'UN', 'defined';
 print qq{scalar context bare return: '$s'};
 $s = Sel();
 print 'scalar empty list ', defined $s ? '' : 'UN', 'defined';
 print qq{scalar context empty list: '$s'};
 @ra = Sbr();
 print qq{list context bare return: (@ra)};
 @ra = Sel();
 print qq{list context empty list: (@ra)};
"
scalar bare return UNdefined
Use of uninitialized value in concatenation (.) or string at ...
scalar context bare return: ''
scalar empty list UNdefined
Use of uninitialized value in concatenation (.) or string at ...
scalar context empty list: ''
list context bare return: ()
list context empty list: ()