my $var = 'world';
printf "Hello %s.\n", $var;             # goes to STDOUT
my $out = sprintf "Hello %s.\n", $var;  # goes to $out

##</code><code>##

my $var = 'world';
format STDOUT =
Hello @>>>>>>>>>>>>>>>
      $var
.
write;                                  # goes to STDOUT
# my $out = swrite;                     # I NEED HELP!