Your formatting standards are probably not optimal for this situation. I have taken the liberty to reformat it somewhat. Also I would propose to change the order always to header - content - footer which makes it a bit more readible as well (unless this has an impact on the output?).

You can also avoid deep nesting by naming a few of the code refs and define them separately.

Here is an illustration of what I mean, I hope this helps.

# non-standard formatting ############################################
+#############################
# always put footer at the end (assuming order does not matter?)
body( header   => sub { hgroup(  sub { }); },
      contents => sub { article( header   => sub { },
                                 contents => sub { section( header   =
+> sub { },
                                                            contents =
+> sub { aside( header   => sub { },
                                                                      
+               contents => sub { }, 
                                                                      
+               footer   => sub { }, ); }, 
                                                            footer   =
+> sub { }, );
                                                   section( header   =
+> sub { },
                                                            contents =
+> sub { }, 
                                                            footer   =
+> sub { }, );
                                                   aside(   header   =
+> sub { },
                                                            contents =
+> sub { }, 
                                                            footer   =
+> sub { }, ); }, 
                                 footer   => sub { }, ); }, 
      footer   => sub { address( sub { }); }, );


# alternative ########################################################
+#############################
# remaining super-structure
body( header   => sub { hgroup(  sub { }); },
      contents => sub { article( header   => sub { },
                                 contents => \&contents1,
                                 footer   => sub { }, ); },
      footer   => sub { address( sub { }); }, );

# delegated content
sub contents1 { section( header   => sub { },
                         contents => sub { aside( header   => sub { },
                                                  contents => sub { },
                                                  footer   => sub { },
+ ); },
                         footer   => sub { }, );
                section( header   => sub { },
                         contents => sub { },
                         footer   => sub { }, );
                aside(   header   => sub { },
                         contents => sub { },
                         footer   => sub { }, ); }
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