*** Evl: Syn ";" {{ Syn ":=" {{ Var "&prefix:hi" (line 1, column 8); sub {...} }
}; App "&prefix:hi" [] [Val (VStr "Perl 6!\n")] }}
***  Evl: Syn ":=" {{ Var "&prefix:hi" (line 1, column 8); sub {...} }}
***  Ret: sub {...}
***  Evl: App "&prefix:hi" [] [Val (VStr "Perl 6!\n")]
***   Evl: Syn "[]" {{ Syn "," {{ "Perl 6!\n" }}; 0 }}
***    Evl: Syn "," {{ "Perl 6!\n" }}
***    Ret: ("Perl 6!\n")
***   Ret: ("Perl 6!\n")
***   Evl: Syn "[]" {{ Syn "," {{ "Perl 6!\n" }}; (1, ...) }}
***    Evl: Syn "," {{ "Perl 6!\n" }}
***    Ret: ("Perl 6!\n")
***   Ret: ()
***   Evl: Syn ";" {{ App "&infix:~" [] [Val (VStr "Hello, "),Var "$_" (line 1,
column 22)] }}
***    Evl: App "&infix:~" [] [Val (VStr "Hello, "),Var "$_" (line 1, column 22)
]
***     Evl: Var "$_" (line 1, column 22)
***     Ret: ("Perl 6!\n")
***     Evl: Syn "[]" {{ Syn "," {{  }}; (0, ...) }}
***      Evl: Syn "," {{  }}
***      Ret: ()
***     Ret: ()
***    Ret: "Hello, Perl 6!\n"
***   Ret: "Hello, Perl 6!\n"
***  Ret: "Hello, Perl 6!\n"
*** Ret: "Hello, Perl 6!\n"
Hello, Perl 6!