If it finds XPath.pm, then I doubt it is being run from a web server. I thought that it might be a permissions problem specific to how the *.dll needs to be loaded, but I've done this same trick in order to allow people to use Tk-based Perl scripts that I've written when many people don't have Tk installed (everyone has Perl installed)

BEGIN {
    my $haveTk= eval { require Tk; 1 };
    if(  ! $haveTk  ) {
        my $perl= "//tye-desk/perl/bin/perl.exe";
        warn "Switching to Tye's copy of Perl since Tk isn't installed
+...\n";
        die "Can't access $perl: $! ($^E)\n"
            unless  -f $perl;
        system( 1, $perl, $0, @ARGV );
        exit( 0 );
    }
}
[download]

and that works even though my "perl" share is read-only. I doubt Perl's own loading of @INC based on the path to perl.exe is any better than "use lib" loading UNCs in the same way (and I just checked and @INC gets loaded with "//tye-desk/...").

I'd probably debug DynaLoader (either just edit DynaLoader.pm or use "perl -d") so that it shows $^E which likely will give a better explanation of why it couldn't load the *.dll file.