Checking return context, beyond wantarray()

shemp has asked for the wisdom of the Perl Monks concerning the following question:

I was just wondering if there is a way to tell if something is expected back from a function call. Let me demonstrate:

   # CASE 1
   my $value = do_something(...);

   # CASE 2
   do_something(...)
[download]

So CASE 1 is what i mean by the call is expecting something back, and CASE 2 is not expecting anything back.

I know of no way to detect this - wantarray() tests for something different. There are probably a number of convoluted subtleties about why this cannot be done, but i have some use for it - mainly for code transition debugging, but i could see other uses for it...

Thanks much.

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Re: Checking return context, beyond wantarray() by mifflin (Curate) on Jul 14, 2004 at 20:21 UTC
Perl Cookbook 10.6 says... `if (wantarray()) { # list context } elsif (defined wantarray()) { # scalar context } else { # void context }` [download]	[reply] [d/l]
Re: Checking return context, beyond wantarray() by ccn (Vicar) on Jul 14, 2004 at 20:21 UTC
wantarray returns undef value in void context (your CASE 2) true in list context defined false in scalar context see perldoc -f wantarray	[reply]
Re: Checking return context, beyond wantarray() by iburrell (Chaplain) on Jul 14, 2004 at 20:21 UTC
wantarray will return undef if the function is called in void context, when the caller is not expecting a value.	[reply]
Re: Checking return context, beyond wantarray() by rjbs (Pilgrim) on Jul 14, 2004 at 20:45 UTC
I suggest you stick with the answers from the other monks -- look more closely at wantarray. However, for when you're feeling goofy (or just need something strange), look at Want. rjbs	[reply]
Re: Checking return context, beyond wantarray() by shemp (Deacon) on Jul 14, 2004 at 20:36 UTC
Thanks much. I guess i thought i knew more than i did about wantarray(), and didnt re-read carefully...flame away	[reply]


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