What language is this finger exercise really in? 
#include <stdio.h>  /* Simple example program to */
#define eval main() /* demo the preprocessor */

eval
{
    printf("Hello world\n");
}

[download]
Of course this is a simple joke. For truly impressive take a look at BooK's The Best Ever. It is a valid PostScript program and also a valid Perl program. Save it to a file and run with Perl or take a look at it with ghostscript. Both will work (though the output will be somewhat different). And what it does is not at all obvious.

In reply to Re (tilly) 1: Challenge : use perl::polylingual by tilly
in thread Challenge : use perl::polylingual by boo_radley

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