I can run this for as long as I like:

#! /usr/bin/perl
use strict;
use warnings;
use threads;

print "threads: ", $threads::VERSION;
print "perl: ", $];
my @child;
my @list =  1 .. 100;

while (1) {
    my @child = map threads->create("test","$_"), @list;
    $_->join for @child;
}

sub test {
    my ($item) = @_;
}
[download]

And the memory usage is rock steady. And that has been true for a long time.

So, what does that tell you?

Your knowledge is out of date. Your platform--be it the pthreads or memory management or whatever--has an underlying problem that cannot be directly addressed by, nor attributed to, Perl. So stop doing that.

BTW: Your "simple reusable threads demo", is way overcomplicated. And always was.