$ perl -wMstrict -e 'BEGIN { package blah; *::x=sub{} } x'
$ perl -wMstrict -e 'BEGIN {               *::x=sub{} } x'
$ perl -wMstrict -e 'BEGIN { package blah; *::x=\$a   } $x++'
$ perl -wMstrict -e 'BEGIN {               *::x=\$a   } $x++'
Variable "$x" is not imported at -e line 1.
Global symbol "$x" requires explicit package name (did you forget to declare "my $x"?) at -e line 1.
Execution of -e aborted due to compilation errors.