$ perl -wMstrict -e 'BEGIN { *::x=sub{} } x'
$ perl -wMstrict -e 'BEGIN { *::x=sub{} } x()'
$ perl -wMstrict -e '      { *::x=sub{} } x()'
$ perl -wMstrict -e '      { *::x=sub{} } x'
Bareword "x" not allowed while "strict subs" in use at -e line 1.
Execution of -e aborted due to compilation errors.
$ perl -wMstrict -e 'x'
Bareword "x" not allowed while "strict subs" in use at -e line 1.
Execution of -e aborted due to compilation errors.
$ perl -wMstrict -e 'x()'
Undefined subroutine &main::x called at -e line 1.
$ perl -wMstrict -e '&x'
Undefined subroutine &main::x called at -e line 1.