This is not Perl, this is shell. When you call the system function, you pass a string that is executed by a shell (usually /bin/sh) just like you called

/bin/sh -c your-command-here
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/dev/null is a special device that acts like a well for your data - it silently eats them and throws them into nowhere. Useful for problems, ain't it? :)

2>&1 redirects standard error (file descriptor 2, where error messages usually are written) to standard output (file descriptor 1, where normal messages are usually printed). I don't know what the Anonymous Monk wanted to do, but I bet that he should change the order of redirections:

... >/dev/null 2>&1
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Otherwise, you'll have errors on the standard output, and the normal standard output thrown away (while I think that he inteded to throw away both of them).

You can learn a bunch of things about the shell viewing the bash man page, anyway.