Be aware of the differences between Coro and threads. Most importantly, Coro is cooperative threads. Only one CPU is used. If any coroutine blocks, so does the entire program.

use strict;
use warnings;
use 5.010;

use Coro;
my @threads;
for my $t ( 1 .. 3 ) {
  push @threads, async {
    print "coro $t says hi $_\n" for 1..3;
  };
}
for (@threads) {
  $_->join;
}
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coro 1 says hi 1
coro 1 says hi 2
coro 1 says hi 3
coro 2 says hi 1
coro 2 says hi 2
coro 2 says hi 3
coro 3 says hi 1
coro 3 says hi 2
coro 3 says hi 3
[download]

Coro has a yield() call which can be used to interleave coroutines. However, libraries that don't call yield() or use other Coro facilities can still block everything.

Also, yield() doesn't involve additional CPUs, so cpu-intensive programs may benefit more from threads or fork().