MacPerl does not convert 'file/path/' to 'file:path:'; one must actually use colons in the paths.

Even trickier, however, is the way of specifying relative paths, by prepending the directory separator. On a Mac, ':mammal:dog' means the file dog in the directory mammal in the current working directory, whereas on Unix '/mammal/dog' means the file dog in the directory mammal in the root directory.

On the other hand, the path 'animal:mammal:dog' on a Mac means the file dog in the directory mammal in the root directory of the volume animal. On Unix 'animal/mammal/dog' means the file 'dog' in the directory 'mammal' in the directory 'animal' in the current working directory.

Here's a script that demonstrates this behavior in MacPerl:

  use Cwd;

  print cwd(), "\n";

  -e 'foo' or mkdir('foo', 0777) or die "Can't mkdir 'foo': $!\n";

  open(FH, '>foo/bar') or warn "Can't open 'foo/bar': $!\n";
    # creates a file named 'foo/bar' in cwd

  open(FH, '>foo:bar') or warn "Can't open 'foo:bar': $!\n";
    # fails, unless you actually have a volume named 'foo'
    # in that case, creates a file named 'bar' on the volume 'foo'

  open(FH, '>:foo:bar') or warn "Can't open ':foo:bar': $!\n";
    # creates a file named 'bar' in the directory 'foo' in the cwd
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Getting cross-platform file paths is not an easy problem. That's why the File::Spec module was created. (Except that all the documentation for the module is in File::Spec::Unix. You'll have to read it locally.)