The IPC::Open docs say:

Since Perl 5.8.0, you can also use the list form of open for pipes : the syntax

open KID_PS, "-|", "ps", "aux" or die $!;
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forks the ps(1) command...

I don't understand the terminology "forks the ps(1) command". As far as I know, a fork() copies the current program and runs it in another process. So how can you "fork() a command"? Doesn't fork() always copy the current program rather than run a specified command? Do the IPC docs really mean a fork(), which copies the current program and runs it in a another process, plus an exec() in the child which replaces the current program with the command?