$ perl -e 'print sprintf( "%s%s",
> "header" . "\n",
> sub { return 3});
> '
header
CODE(0x6000684c8)

##</code><code>##

$  perl -e 'print sprintf( "%s%s", "header"  . "\n", ,sub { return 3}->())'
header
3

##</code><code>##

$ perl -e 'sub concat { my $str; for ($_[0]..$_[1]) { $str .= $_;} $str;}
> print  sprintf "%s\n%s\n",  "foo", concat('a', 'e');
> '
foo
abcde