Dude :) yes really

When you install modules that install perl "EXE_FILES" their shebang gets rewritten to point to the perl doing the installing

If you uninstall/remove/delete... that perl but the "EXE_FILE" that was installed using that perl remains ... this case your "cpan" file ... then its probably pointing to the wrong perl, one which doesn't exist ... thus the error message ( from your shell )

So, cheapest way to fix it, is remove the offending file

At this point, if the other perl is in your path, trying to execute cpan should call the new perls cpan file which will have the correct shebang for the new perl and call the correct perl

If this isn't the case, and there just is no cpan file anymore, this is where reinstalling CPAN module comes in, it will install cpan EXE_FILE with correct shebang

You can always look inside the "cpan" file you're trying to execute to see the paths it contains

cpan probably isn't the only file with the wrong shebang