All you do is drop your thread code block into a forked child's code block. Not recomended, but the simplest is:

if(fork() == 0){exec("command")}
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but that dosn't watch for zombies, or limit the number of forks at any one time.

Usually, you do something like:

#!/usr/bin/perl

# There is a limit to the number of child processes you can 
# have, or should want, so big jobs may require the kind of 
# throttling Parallel::ForkManager gives you.
#The receipe for 100 processes:

#avoid zombies
$SIG{CHLD} = 'IGNORE';  # check if it works on your system
  
  for (1..100) {
       my $pid = fork;
             next if $pid;            # in parent, go on
             warn($!), next
     if not defined $pid;  # parent, fork errored out
       exec @cmd;               # in child,
       #   go do @cmd and don't come back
}
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There are a bunch of recipes around for limiting the number of forks running at any one time, but you are best off using Parallel::ForkManager See: controlling child processes