Thanks!

The reason I used warn with the newline "$/" is that without it, you get a lot of extra clutter:

1 at x.pl line 2.
2 at x.pl line 2.
3 at x.pl line 2.
5 at x.pl line 2.
7 at x.pl line 2.
11 at x.pl line 2.
13 at x.pl line 2.
17 at x.pl line 2.
19 at x.pl line 2.
23 at x.pl line 2.
29 at x.pl line 2.
31 at x.pl line 2.
...
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but, come to think of it, that's a moot point your case, because of the switches you're using to Perl.

As far as the golfiest version ... well, you never know. :-)  Here's another example I just thought of which uses the non-newline "warn", but is only 41 characters:

++$x;{map$x%$_||redo,2..$x++;warn$x;redo}
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So if you wanted to, you could do something like:

/usr/bin/perl '-le$x=1;{map$x%$_||redo,2..$x++;print$x;redo}'
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But in the end, the important thing is that whatever you decide to use, you've chosen a signature which fits your unique style and taste.  Thanks for giving us a chance to be a part of the process!