> perl -w
use strict;
BEGIN { *x= \$foo::y; }
print $x;
Variable "$x" is not imported at - line 3.
__END__
Global symbol "$x" requires explicit package name at - line 3.
Execution of - aborted due to compilation errors.

 > perl -w
use strict;
BEGIN { package foo; *main::x= \$foo::y; }
print $x;
__END__
Name "foo::y" used only once: possible typo at - line 2.
Use of uninitialized value in print at - line 3.