Strange behaviors in rx interpolation

rxinterp.pm

grammar gram {
	my @stuff1 = rx/12/, rx/'='/, rx/<gram::foo>/;
	my @stuff2 = rx/12/, rx/'='/, rx/bar/;

        rule foo {bar};

        regex s1a { @stuff1* % ' '}
        regex s1b { <@stuff1>* % ' '}
	regex s2a { @stuff2* % ' '}
        regex s2b { <@stuff2>* % ' '}

        regex q1a { @stuff1* }
        regex q1b { <@stuff1>* }
	regex q2a { @stuff2* }
        regex q2b { <@stuff2>* }
}

say so gram.parse('12 = bar', :rule<s1a>); # Works and should fail
say so gram.parse('12 = bar', :rule<s1b>); # Fails and should work
say so gram.parse('12 = bar', :rule<s2a>); # Works and should fail
say so gram.parse('12 = bar', :rule<s2b>); # Works as it should

say so gram.parse('12=bar', :rule<q1a>); # Works and should fail
say so gram.parse('12=bar', :rule<q1b>); # Works as it should
say so gram.parse('12=bar', :rule<q2a>); # Works and should fail
say so gram.parse('12=bar', :rule<q2b>); # Works as it should