Re^2: Why does system("mv $x $y") not work when it works at the command line?

This varies by shell. By default zsh will gripe if it can't find a match (although I think there's options enabled with setopt which will make it behave more like POSIX/ksh). For example the first works (because of course there's a file named foo . . . who doesn't have one?) but the second errors first and doesn't actually run the echo command.

oscar:~  1064> echo fo[ob]
foo
oscar:~  1065> echo fo[xy]
zsh: no matches found: fo[xy]
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The cake is a lie.
The cake is a lie.
The cake is a lie.

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