Depending on $Config{dlext} doesn't work in all cases.

[plicease]

For example, FFI::Platypus::Lang::Pascal fails like this on OS X:

/usr/local/bin/fpc -Px86_64 myunit.pas
Free Pascal Compiler version 2.6.4 [2014/02/26] for x86_64
Copyright (c) 1993-2014 by Florian Klaempfl and others
Target OS: Darwin for x86_64
Compiling myunit.pas
Assembling (pipe) myunit.s
57 lines compiled, 0.1 sec 
/usr/local/bin/fpc -Px86_64 test.pas
Free Pascal Compiler version 2.6.4 [2014/02/26] for x86_64
Copyright (c) 1993-2014 by Florian Klaempfl and others
Target OS: Darwin for x86_64
Compiling test.pas
Assembling (pipe) test.s
Linking libtest.dylib
8 lines compiled, 0.1 sec 
no dylib in /Users/ollisg/.cpanm/work/1422984005.6881/FFI-Platypus-Lang-Pascal-0.01/libtest at lib/Module/Build/FFI/Pascal.pm line 187.
FAIL
! Installing FFI::Platypus::Lang::Pascal failed. See /Users/ollisg/.cpanm/work/1422984005.6881/build.log for details. Retry with --force to force install it.
urquhart% ls libtest
libtest.dylib*  myunit.o  myunit.pas  myunit.ppu  test.o  test.pas

because fpc produces a .dylib instead of a .bundle.

%Config disappoints again.

[plicease]

should update FFI::Util as well.