In fact, perl6.exe contains some dependencies on build tree. Just after a build, perl6.exe works :
D:\parrot-0.8.0-devel>bin\perl6 -v This is Rakudo Perl 6, revision 32151 built on parrot 0.8.0-devel for MSWin32-x86-multi-thread. Copyright 2006-2008, The Perl Foundation. But, after a 'make realclean' in build tree, it fails : D:\parrot-0.8.0-devel>bin\perl6 -v "load_bytecode" couldn't find file 'P6object.pbc' current instr.: 'onload' pc 0 (src/gen_builtins.pir:28) called from Sub 'parrot;Perl6;Compiler;main' pc -1 ((unknown file):-1) François.