We are off of my main point!
The return value of sprintf() means nothing in this context, but it will returned absent an explicit return statement. Why return a string that the caller doesn't care about and means nothing as opposed to returning a more simple undef value? I am simply saying that I prefer having explicit return values. What your post said is "correct". Please do not take this as any real argument. We are talking about a very fine point here, not any real criticism.

Ok, I see the situation better now.
I would have written  return sprintf "...."
That is just a matter of coding style. Not any real "problem".

Why return a string that the caller doesn't care about and means nothing as opposed to returning a more simple undef value?

Excuse me? this string is what the caller requests by calling the function create_snapshot_name() which was written for this very purpose. The calling line is

  my $snap_name = create_snapshot_name();
[download]

in function take_new_snapshot() and the name of the variable in which this return value is stored also indicates that a string is expected as return value from that function.

I am simply saying that I prefer having explicit return values.

I had those discussions before, and I stick to the perl way: a subroutine returns, absent early returns, the result of the last computed expression, with or without explicit return statement. Were I to work with you having a coding policy in place which requires always stating explicit returns, I would do likewise, otherwise not.

Edit:

Well, depends. If I was to concoct a function dependent on context for its return value, I'd use explicit returns, sometimes setting $@ if something failed. But it really boils down to two possibilities for return values as a subroutine:

1. I know what I have, and this is what you get, and might honour your context.
2. take that bastard, you get what you asked for

But then, for case 1, I would have to raise an exception if I have a list and am called in scalar context. Or should I? maybe they want just the number of elements? and vice versa.

perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'

In Perl, if printf() fails, a fatal error will be thrown long before it returns to the caller.

wrong

I've never checked the return value of sprintf.

then stop talking and read sprintf

I disagree about printf() errors.
With normal file operations, what I said is true. It is almost impossible for a print or printf to "fail" once a local Hard Disk file handle is open. One way would be "File system full", but in that case, a fatal exception is thrown - the calling program won't see that.

I did make a mistake in interpreting the exact situation. I would have written: return sprintf "..." because I favor explicit return statements.