Grammar succeeds once Grammar::Tracer is imported

weird.txt

$ perl6 -e 'grammar G { regex TOP { [<x> ['\'';'\'' | $$] \s*]* }; token x { B | \s* <y> \s* '\''()'\''* }; regex y { A | B } }; my $s = "B\nA();"; say ?G.parse($s)'
False

$ perl6 -e 'use Grammar::Tracer; grammar G { regex TOP { [<x> ['\'';'\'' | $$] \s*]* }; token x { B | \s* <y> \s* '\''()'\''* }; regex y { A | B } }; my $s = "B\nA();"; say ?G.parse($s)'
TOP
|  x
|  * MATCH "B"
|  x
|  |  y
|  |  * MATCH "A"
|  * MATCH "A()"
|  x
|  |  y
|  |  * FAIL
|  * FAIL
* MATCH "B\nA();"
True