>perl -wMstrict -le
"print level2();
 sub level1 {
   sub level2 { return 'level2(): foo' }
   print 'level1(): ', level2();
   }
 level1();
 print level2();
"
level2(): foo
level1(): level2(): foo
level2(): foo

##</code><code>##

>perl -wMstrict -le
"sub level1 {
   my $x = shift || 'default';
   local *foo = sub { return 'foo' . $x };
   print foo();
   }
 level1('bar');
 level1();
 foo();
"
foobar
foodefault
Undefined subroutine &main::foo called at -e line 1.