I get real nervous wading into these more subtle issues, so flame if you must but I am just trying to understand.

My question is, based on the code below, is the problem in how you test for an empty list ??. Because if I am reading the output from below correctly an undefined @x and a @x = () will both return 0 when @x is tested for length.

I do find it curious that a an undefined array returns 0 when asked scalar @x.

So in conclusion in order to test if @x or an empty list one must test for both definedness and length ??

Of course I may have just wasted your time and mine beating a dead horse if I have I will meditate on perldoc:perldata for an extra hour tonight. 

# x not defined
print "X not defiined:\t ",scalar @x,"\n" if (!defined(@x));
# given an empty list
@x = x();
print "X empty list:\t ",scalar @x,"\n";
@x = (1,2,3);
# x given a populated list
@x = x();
print "X populated:\t ",scalar @x,"\n";

sub x () {
  return @x if defined(@x) and warn "\@x was already defined";
  return @x if (scalar @x==0) and warn "\@x is 0";
  return wantarray ? () : undef;
}


Output:
X not defiined:  0
@x is 0 at wa.pl line 14.
X empty list:    0
@x was already defined at wa.pl line 13.
X populated:     3

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MitD -- Made in the Dark
'My favourite colour appears to be grey.'

In reply to Re: Empty list as a return value by mitd
in thread Empty list as a return value by princepawn

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