OHHHH! I completely missed the fact that you're using a packager. I thought pp was referring to "pretty print" (which is what your code does). What can I say? I use xml_pp quite often.

@XML::Parser::Expat::Encoding_Path is built from @INC. I bet that the problem is that your packager puts a callback function in @INC instead of the path to the files.

Assuming pp actually extracts the files to some directory, you can do:

BEGIN {
    my $path_to_enc_files = ...;
    $path_to_enc_files =~ s{/XML/Parser/Encodings/?\z}{};
    local @INC = ( @INC, $path_to_enc_files );
    require XML::Parser::Expat;
}
[download]

According to almut's post, that boils down to

BEGIN {
    local @INC = ( @INC, $ENV{PAR_TEMP} );
    require XML::Parser::Expat;
}
[download]

Place this before the first use XML::Parser::Expat;