You seem to be leaping through extraordinary hoops in order to achieve what happens naturally on my system:

C:\test>p1
[0] Perl> print $0;;
C:\Perl64\bin\p1.pl

[0] Perl> print $^X;;
C:\perl64\bin\perl.exe
^C

C:\test>cd \Perl64\bin
C:\Perl64\bin>.\p1.pl

[0] Perl> print $0;;
C:\Perl64\bin\p1.pl

[0] Perl> print $^X;;
C:\perl64\bin\perl.exe
[download]

And under both the above circumstances, ProcessExplorer shows the fully qualified path of both the perl executable and the script being run.

Do you know of circumstances where that is not the case?