% perl -v

This is perl, v5.6.0 built for i686-linux

   [snip]

% perldoc perldelta

   [snip]

       exists() is supported on subroutine names
 
       The exists() builtin now works on subroutine names.  A
       subroutine is considered to exist if it has been declared
       (even if implicitly).  See the exists entry in the
       perlfunc manpage for examples.

   [snip]