My thanks to those who are suggesting Windows 7 is not knowing which program to associate with a .pl file. However, from the shown results we can surmise that the system finds C:\Perl\bin\Perl.exe on it's own and executes the short .pl script. It therefore knows the correct association. It just does not set ARGV correctly. Just as a check, I looked at the Default Programs as suggested and it does indeed say .pl is set to the "Perl Command Line Interpreter".

Hmmm. Activestate wanted to install Perl into C:\Perl64. I told it to install it to C:\Perl instead. Maybe that is the problem. I will try to move C:\Perl elsewhere and reinstall the latest Perl to C:\Perl64.

Time passes ...

Okay, I just uninstalled and then reinstalled Perl. The problem went away. Thank goodness.