Why is a threaded version of this particular Perl script 200 times slower than its non-threaded counterpart?

Question

A presentation by Mikhael Goikhman from a 2003 Perl conference includes a pair of examples of prime-number-finding scripts. One is threaded, and the other is not. Upon running the scripts (print lines commented out), I got an execution time of 0.011s on the non-threaded one, and 2.343 (!) seconds on the threaded version. What accounts for the stunning difference in times?

I have some experience with threads in Perl and have noticed before that thread creation times can be particularly brutal, but this doesn't seem to be the bottleneck in Goikham's example.

Answer 1

Jay P. is right:

~$ strace -c ./threads.pl
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 99.80    0.116007       10546        11           futex
  0.20    0.000229           6        36           mmap2
  0.00    0.000000           0        31           read
  0.00    0.000000           0        49        13 open
  0.00    0.000000           0        36           close

Compare that with:

~$ strace -c ./no-threads.pl
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 90.62    0.000261         261         1           execve
  9.38    0.000027           0       167           write
  0.00    0.000000           0        12           read
  0.00    0.000000           0        38        13 open
  0.00    0.000000           0        25           close