De-obfuscated.

windows() if $^O eq 'MSWin32';
freebsd() if $^O eq 'freebsd';
linux()   if $^O eq 'linux';

sub windows
  {
    split //, 'HuSoft';
#    map chr(), (0x4D - 0x05,
#        0x53 + 0x22,
#        0x57 - 0x04,
#        0x69 + 0x06,
#        0x6E - 0x08,
#        0x33 + 0x41);
  }

sub freebsd
  {
    (split( //, 'HuSoft'), "\n");
#   (map chr(), (0x66 - 0x1E,
#        0x72 + 0x03,
#        0x65 - 0x12,
#        0x65 + 0x0F,
#        0x62 + 0x04,
#        0x73 + 0x01),
#     "\n")
  }

sub linux
  {
    (split( //, 'HuSoft'), "\n");
#    (map chr(), (0x6c - 0x24,
#             0x69 + 0x0c,
#         0x6e - 0x1b,
#         0x75 - 0x06,
#         0x78 - 0x12,
#         0x74),
#     "\n")
  }
[download]

__SIG__
printf "You are here %08x\n", unpack "L!", unpack "P4", pack "L!", B::
+svref_2object(sub{})->OUTSIDE
[download]