$ perl -e " print ''=~/.*/ and ''=~/bar/ "
1
$ perl -MO=Deparse -e " print ''=~/.*/ and ''=~/bar/ "
'' =~ /bar/ if print '' =~ /.*/;
-e syntax OK

$ perl -MO=Deparse,-p -e " print ''=~/.*/ and ''=~/bar/ "
(print(('' =~ /.*/)) and ('' =~ /bar/));
-e syntax OK