Add CPAN Butterfly Plan references

- endprotoent, getprotobyname, getprotobynumber, getprotoent, setprotoent
- __FILE__, __LINE__, __PACKAGE__, __SUB__

Author: lizmat

doc/Language/5to6-perlfunc.pod6

@@ -511,7 +511,11 @@ Appears not to be in Perl 6.
 
 =item __FILE__
 
-Replaced by C<$?FILE>.
+Replaced by C<$?FILE> which is slightly different from C<__FILE__> in that
+it is always an absolute path, rather than a relative one in the Perl 5 case.
+
+The Perl 6 ecosystem has a module C<P5__FILE__> which exports a C<__FILE__>
+term that mimics the original Perl 5 behaviour as much as possible.
 
 =head2 fileno
 
@@ -641,25 +645,30 @@ C<endservent>, C<getservent>, C<getservbyname>, C<getservbyport> and
 C<setservent> functions that mimic the original Perl 5 behaviour as much
 as possible.
 
-=item gethostbyname NAME
+=item endprotoent
 
 =item getprotobyname NAME
 
-=item gethostbyaddr ADDR, ADDRTYPE
-
 =item getprotobynumber NUMBER
 
-=item gethostent
-
 =item getprotoent
 
-=item sethostent STAYOPEN
-
 =item setprotoent STAYOPEN
 
-=item endhostent
+The Perl 6 ecosystem has a module C<P5getprotobyname> which exports the
+C<endprotoent>, C<getprotoent>, C<getprotobyname>, C<getprotobynumber> and
+C<setprotoent> functions that mimic the original Perl 5 behaviour as much
+as possible.
 
-=item endprotoent
+=item gethostbyname NAME
+
+=item gethostbyaddr ADDR, ADDRTYPE
+
+=item gethostent
+
+=item sethostent STAYOPEN
+
+=item endhostent
 
 [NEEDS FURTHER RESEARCH] Apparently this range of functions are to be handled
 by roles like User, Group, etc.
@@ -858,6 +867,9 @@ function that mimics the original Perl 5 behaviour as much as possible.
 
 Replaced by C<$?LINE>.
 
+The Perl 6 ecosystem has a module C<P5__FILE__> which exports a C<__LINE__>
+term that mimics the original Perl 5 behaviour as much as possible.
+
 =head2 link
 
 =item link OLDFILE, NEWFILE
@@ -1122,7 +1134,12 @@ directly in Perl 6.
 
 =item __PACKAGE__
 
-Replaced by C<$?PACKAGE>.
+Replaced by C<$?PACKAGE> which is slightly different from C<__PACKAGE__> in
+that it is the actual package object.  You should call the C<.^name> method
+on it to get a string.
+
+The Perl 6 ecosystem has a module C<P5__FILE__> which exports a C<__PACKAGE__>
+term that mimics the original Perl 5 behaviour as much as possible.
 
 =head2 pipe
 
@@ -1765,7 +1782,12 @@ L<functions|/language/functions>.
 
 =item __SUB__
 
-Replaced by C<&?ROUTINE>.
+Replaced by C<&?ROUTINE> which is slightly different from C<__SUB__> in
+that it is the actual C<Sub> (or C<Method>) object.  You should call the
+C<.name> method on it to get a string.
+
+The Perl 6 ecosystem has a module C<P5__FILE__> which exports a C<__SUB__>
+term that mimics the original Perl 5 behaviour as much as possible.
 
 =head2 substr