I proceeded along the other path, as pr. the ActiveState instructions. The ppm upgrade resulted in a number of 'ordering conflicts', which I was able to resolve using the AS PPM application to reinstall the packages in question :
C:\Perl>ppm upgrade
ppm upgrade failed: No ordering between package Perl6-Currying-0.05 and Perl6-Currying
ppm upgrade failed: No ordering between package Term-ReadLine-Perl-1.0302 and Term-ReadLine-Perl
ppm upgrade failed: No ordering between package libwww-perl-5.808 and libwww-perl
ppm upgrade failed: No ordering between package psh-1.8.1 and psh
ppm upgrade failed: No ordering between package Digest-MD4-1.5 and Digest-MD4-1.5-r1

These ordering conflicts are probably a result of not having cleaned up obsolete ppm versions before reinstalling new ones; I can't blame that on the AS upgrade procedure as such

After a succesfull ppm upgrade, there were still a number of 5.8 packages missing in the 5.10 upgrade installation (eg. Win32, Win32-IE-Mechanize, GD and others). These - it seems - are not (yet) included in the AS repository, and will have to be installed from other ppm repositories in the Perl community. The problem here is, that these ppms are not (yet) 5.10 'compliant'...

At this point in the procedure I chose to 'fall back' on a 5.8 installation (I *had* done a backup of the Perl 5.8 \site \lib, \bin and \html directories :).

I think I'll aim at installing 5.10 in parallel with 5.8 (as recommended above by fellow reverend monks), and use 5.10 for future projects, as the needed ppm-packages get available for the latest Perl.

Allan