[MacPerl] A puzzling sprintf error

[Vic Norton]

The code

    #!perl -w
    $x = 0.061234567;
    $string = sprintf "%.2f\%", $x * 100;

works fine ($string = 6.12%), but it produces an

   Invalid conversion in sprintf: end of string

error message. Removing the -w flag eliminates the error message, but 
I don't understand why there is an error at all. Obviously "\%" is 
the source of the error, but why should this literal %-sign cause a 
problem?

I'm not interested in a get-around. The line

    $string = sprintf( "%.2f", $x * 100 ) . '%';

works fine. I'm just curious as to why the first form results in an 
error message.

Regards,

Vic