Emacs org mode: how to create literate programs with noweb syntax - emacs

Question

I am trying to create this Perl program:
#!/usr/bin/perl
use strict;
use warnings;
open(my $fh, "<", "test.txt")
or die "cannot open < file name: $!";
while (my $line = <$fh>) {
print $line;
}
close($fh);
I created this org file:
#+BABEL: :cache yes :tangle yes :noweb yes
#+NAME: top_block
#+begin_src perl :tangle test.pl
#!/usr/bin/perl
use strict;
use warnings;
open(my $fh, "<", "test.txt")
or die "cannot open < file name: $!";
<<output all the lines from file>>
close($fh);
#+end_src
#+NAME: output all the lines from file
#+begin_src perl :tangle test.pl
while (my $line = <$fh>) {
print $line;
}
#+end_src
But it created this:
empty line here
#!/usr/bin/perl
use strict;
use warnings;
open(my $fh, "<", "test.txt")
or die "cannot open < file name: $!";
<<output all the lines from file>>
close($fh);
while (my $line = <$fh>) {
print $line;
}
Problems:
There is an empty line at the top of the file.
Noweb block wasn't expanded, but put to the bottom of the file.
I don't understand, how to write the output file name once at the top? Currently, I have to rewrite it for every block: :tangle test.pl.

Answer 1

Here is the solution:
#+BABEL: :cache yes :tangle yes :noweb yes
#+NAME: top_block
#+begin_src perl :tangle "test.pl" :noweb tangle :shebang #!/usr/bin/perl
use strict;
use warnings;
open(my $fh, "<", "test.txt")
or die "cannot open < file name: $!";
<<output-all>>
close($fh);
#+end_src
#+NAME: output-all
#+begin_src perl
while (my $line = <$fh>) {
print $line;
}
#+end_src
To put #!/usr/bin/perl to the top line use :shebang #!/usr/bin/perl
Noweb blocks names shouldn't contain spaces. Replace them with "-".
Write the file name for the root noweb block.