{
  package foo;
  ...
}
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In addition, prior to 5.14 (and even post-5.14) this idiom terminated the scope of the enclosed package, which was (and is) very useful.

>perl -wMstrict -le
"{ package Foo;
   sub my_pkg { print 'works pre-5.14: ', __PACKAGE__; }
   }
 ;;
 package Bar {
   sub my_pkg { print 'post-5.14: ', __PACKAGE__; }
   }
 Foo::my_pkg();
 Bar::my_pkg();
 print __PACKAGE__;
"
works pre-5.14: Foo
post-5.14: Bar
main
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Update: Expanded code example.