Sometimes, you want a system(), but you want the child to have a different current directory, environment, Standard Input/Output/Error, or whatever normally gets inherited by a fork. The trick is to emulate the system() with slightly lower-level calls, and then insert your code for changes where only the child executes it. Here's a sample skeleton (from when I was answering a question).
# replacing system("date") with:
defined(my $pid = fork) or die "Cannot fork: $!";
unless($pid) { # I'm the child
  # make your env changes here
  # you can also change directory, umask, priority, etc.
  exec "date";
  die "date not found (just like me last friday night)";
}
# parent continues here...
{
  # to emulate system(), we need to ignore INT and QUIT
  # while the kid is foreground
  local $SIG{INT} = local $SIG{QUIT} = 'IGNORE';
  waitpid($pid, 0);
}

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In reply to open-coding a system() operation by merlyn

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