I lookoed at the code for using the field sep and it tests fine. I ran the program a few more times:

 ./time_print 
Benchmark: running field sep, join, map, each for at least 3 CPU seconds...
 field sep:  4 wallclock secs ( 3.15 usr +  0.01 sys =  3.16 CPU) @ 53475.95/s (n=168984)
      join:  4 wallclock secs ( 3.15 usr +  0.00 sys =  3.15 CPU) @ 1300.00/s (n=4095)
       map:  3 wallclock secs ( 3.12 usr +  0.00 sys =  3.12 CPU) @ 302.88/s (n=945)

each time on my maching the field sep is really fast.
I changed the map to map {"$_\n"} @array for these runs