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Perl portability is a bigger subject than your meditation gives credit for. Although to my mind you have just scratched the surface, I fully approve of your meditation, and any call to arms on portability.
I have spoken about this subject at several YAPC conferences, workshops and perlmonger tech talks, see http://www.ivorw.com/talks/perlport.ppt. You're welcome to use any material from these slides, suitably acknowledged. You can quote the URL as I have no plans to move it. Also, if you have any feedback or corrections, please let me know.
Some specific comments
Section 1.2 is not correct - it's not just a case of the direction of your slashes, but whether your filename is using native syntax or POSIX syntax. Have a look at VMS filenames for a bizarre native syntax.
When it comes to running perl scripts and one-liners on Windows, pl2bat is worth a mention, as is PAR. Also, on Windows I nearly always turn off the file association between .pl and perl, as usually when browsing directories and websites, I don't want to run a .pl, I want to look at it.
In reply to Re: RFC: A Primer on Writing Portable Perl Programs