Don't use PerlApp; therefore, don't know if this is relevant, but since your messages include a reference to the --add command

File\Spec\Unix.pm:
warn: auto\File\Spec\Unix\Unix.dll not found
refby: perlapp --add
....

from the AS doc re PerlApp9.3 here's some possibly relevant information:

---

--add modules
    List additional modules to include in the application. PerlApp also attempts to include 
    modules that the listed modules depend on. Multiple modules can be separated by whitespace 
    or a semicolon. This option can be repeated. For example: 

        perlapp myscript.pl --add IO::Socket --add XML::Parser::Expat

    ...would include IO::Socket and XML::Parser in your application.

    The --add option supports the following wildcard notations: --add Module::* includes Module::Foo, 
    but neither Module itself nor Module::Foo::Bar. --add Module::** includes Module::Foo and 
    Module::Foo::Bar, but not Module. --add Module:: works the same as --add Module;Module::**, 
    including all of Module, Module::Foo and Module::Foo::Bar. Note that you may have to quote 
    the * character to prevent wildcard expansion by your command shell.

    PerlApp uses built-in heuristics to determine any additional modules that may be required at 
    runtime. When building an executable, missing modules are displayed as errors. In a few cases, 
    however, the heuristics are used to downgrade errors to warnings. PerlApp issues warnings 
    for the following:

      + Windows executables built without Unix, Mac, VMS and OS/2 modules 
        ....

A bit more information about your script and source might win you better help from those more knowledgable of PerlApp than I.