Things you may want to know:

• To fill @baton:

  my @baton = qw(| \ - /);
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• 1 second seems kinda too much:

  select undef, undef, undef, .15;  # or use Time::HiRes
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• slightly more inefficient, but (cleaner and) in this context I doubt it cares:

  push @baton, shift @baton;
  print "$baton[0]\b";
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How can I start the twirling baton in Perl and then suspend it when I need to execute a system call to run the shell script in Perl?

If I understand your question correctly, which I'm totally unsure about, you may want to read up on $SIG{ALRM}.