$ perl -MO=Deparse -e "  sub foo (&) {}; foo sub{;;}   || 7 "
Type of arg 1 to main::foo must be block or sub {} (not null operation) at -e line 1, at EOF
-e had compilation errors.
sub foo (&) {

}
&foo(sub {

}
 || 7);

$ perl -MO=Deparse -e "  sub foo (&) {}; foo sub{;;}   // 7 "
Type of arg 1 to main::foo must be block or sub {} (not null operation) at -e line 1, at EOF
-e had compilation errors.
sub foo (&) {

}
&foo(sub {

}
 // 7);