gistfile1.txt

grammar Goo {                                                                                                                                                               
    rule TOP { <Foo>+ }                                                                                                                                                     
    rule Foo { 'foo' <Num> <Bar>+ }                                                                                                                                         
    rule Bar { 'bar' <Num>+ }                                                                                                                                               
    rule Num { \d+ }                                                                                                                                                        
}                                                                                                                                                                           
                                                                                                                                                                            
class GooActions {                                                                                                                                                          
    method Bar ($/) {                                                                                                                                                       
        say "This Bar is contained in a Foo whose Num is ???";                                                                                                              
    }                                                                                                                                                                       
}                                                                                                                                                                           
                                                                                                                                                                            
Goo.new.parse(                                                                                                                                                              
    'foo 111 bar 2 3 bar 4 foo 222 bar 5 6',                                                                                                                                
    :actions(GooActions.new)                                                                                                                                                
);                                                                                                                                                                          
                                                                                                                                                                            
#`(                                                                                                                                                                         
                                                                                                                                                                            
    How can I get the Bar action method to see its Foo container                                                                                                            
    rule's Num, to have this printed?:                                                                                                                                      
                                                                                                                                                                            
        This Bar is contained in a Foo whose Num is 111                                                                                                                     
        This Bar is contained in a Foo whose Num is 111                                                                                                                     
        This Bar is contained in a Foo whose Num is 222                                                                                                                     
)                                                                                                                                                                           

You can use a dynamic variable to propagate the desired information down into the nested rules:

grammar Goo {
    rule TOP { <Foo>+ }
    rule Foo { :my $*FOO; 'foo' <Num> { $*FOO = $<Num> } <Bar>+ }
    rule Bar { 'bar' <Num>+ }
    rule Num { \d+ }
}

class GooActions {
    method Bar ($/) {
        say "This Bar is contained in a Foo whose Num is $*FOO";
    }
}

Goo.new.parse(
    'foo 111 bar 2 3 bar 4 foo 222 bar 5 6',
    :actions(GooActions.new)
);