merlyn, thanks for pointing out how to force list interpretation for system.

I think my /bin/foo bar example was a red herring. A better example of what I would like to see perl discourage is the the following use of system to execute a single command:

  system("cmd $with $some $args")
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Because the argument is subject to shell interpretation, this code exposes itself to just too many pitfalls. If we saw this in someone else's code we'd clearly point out that it's unsafe.

If you really want to subject your string to shell interpretation, why not just explicitly call the shell?

It's good that perl provides a way to force list context with system. However, I'll argue that it isn't getting used when it needs to. Users are introduced to this:

system("/bin/ls");   # run /bin/ls with no arguments
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and they generalize to:

system($cmd);        # run the $cmd command with no arguments
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not:

system {$cmd}, $cmd;
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Even when we tell them to use the list version of system to safely preserve passed arguments, they can be in for a surprise. They see this:

system($cmd, $with, $some, $args);
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and generalize to:

system($cmd, @args);
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and then wonder why it doesn't work as expected when @args is the empty list.