Oh, now I notice that you've mixed your coding metaphors a bit.

    my $cmd = "env APPLEJACK=TRUEBLUE $^X $0";
...
    exec($cmd, @ARGV);
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By using the 'list' form of exec, you've told Perl to interpret $cmd as only a path to an executable, not as some string to be interpreted by a shell as 4 different words.