$ perl -E'
   rand;
   my $pid = fork;
   srand if $ARGV[0];
   say rand;
   waitpid($pid, 0);
' 0
0.458778299481736
0.458778299481736

$ perl -E'
   rand;
   my $pid = fork;
   srand if $ARGV[0];
   say rand;
   waitpid($pid, 0);
' 1
0.656664192517386
0.153404296449484