Thank you! Your response made me check %pathext% where .pl is missing: 
C:>echo %pathext%
.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC

[download]

Of course, with no cygin (nor GNUtils) I have no grep or which but pursuing your other suggestions I ran across (BTW, en route, a suggestion to use setx PATHEXT=%PATHEXT%;.PL turned out to be invalid syntax - perhaps omitted from Win7, to judge by MS's documentationNote 1) a MS support page which referred me... which referred me... etc... eventually to what may be a fix but which requires a reboot... so:

--more to come -- after the reboot :-(

Updated, post reboot:

Yech, way too much stumbling around in the dark. But START|COMPUTER|ADVANCED SYSTEM SETTINGS|(System Properties|ADVANCED (tab)|Environmental Variables| leads to a box where one can edit PATHEXT (to add the ".PL")

Note 1 for earlier versions of Win, set ... was documented as valid ONLY for the session in which it was executed.

See also Re: Out of date over <> and 5.10 et seq where ikegami, BrowserUK, tye and Corion discuss quirks, peculiarities, ASSOC decisions by MS and AS's implementation of its use.

But recognize: adding .PL; .pl to %PATHEXT% was NOT a silver bullet; so I have more to seek/do, but this is already waaay too long, but one can hope others, similarly troubled may find some of this useful... so, some keys:

'@ARGV failure' '<>' 'Association' 'PATH' 'PATHEXT'

In reply to Re^2: Win7, ASSOCiation , and @ARGV by ww
in thread Win7, ASSOCiation , and @ARGV by ww

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