The Perl Toolchain Summit needs more sponsors. If your company depends on Perl, please support this very important event.
%token D S 
%tree

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p:
      %name P
      ds ';' ss
    | %name SS
      ss 
;
ds:
      %name D2
      ds ';' D
    | %name D1
      D 
;
ss:
      %name S2
      S ';' ss
    | %name S1
      S 
;

%%