my $pid1 = background("command > some-file");
my $pid2 = background("other-command > some-other-file");

my $tail_pid = background("tail -f some-file");
...do stuff...
if (waitpid $pid1) { kill 9, $tail_pid; }
...

sub background {
  defined(my $pid = fork) or die "unable to fork: $!";
  if ($pid == 0) { exec(@_); exit 1 }
  $pid;
}