C:\Windows\system32>perl -e "use warnings; sub x{@_} print x(substr undef,0)"
Use of uninitialized value in subroutine exit at -e line 1.


C:\Windows\system32>perl -de0

Loading DB routines from perl5db.pl version 1.37
...

  DB<1> use warnings; sub x{@_} print x(substr undef,0)


  DB<2> print $]
5.016003