This should only change "foo" into "zippo" on lines that contain the word "look"
rak --modify-files §look --and='*.subst("foo","zippo",:g)' doc --dont-catch
No lexical found with name '$*_'
in block at EVAL_0 line 1
in block at /Users/liz/Github/rakudo/install/share/perl6/site/sources/70C6A88A4D24E5AE8D2D1FD9DDAE8F61E67B8304 (rak) line 489
in sub rak at /Users/liz/Github/rakudo/install/share/perl6/site/sources/70C6A88A4D24E5AE8D2D1FD9DDAE8F61E67B8304 (rak) line 1412
in sub run-rak at /Users/liz/Github/rakudo/install/share/perl6/site/sources/A3305D8B080035788ADEC2CA92D678DF9712BE6E (App::Rak) line 711
in sub action-modify-files at /Users/liz/Github/rakudo/install/share/perl6/site/sources/A3305D8B080035788ADEC2CA92D678DF9712BE6E (App::Rak) line 3272
This should only change "foo" into "zippo" on lines that contain the word "look"