#! perl -slw
use strict;
use threads;
use threads::shared;

our $N ||= 100;
our $M ||= 2e6;

my %hash : shared;

sub process {
    my $tid = threads->self->tid;
    for( 1 .. $N ) {
        for( keys %hash ) {
            lock( %hash );
            printf "$tid: (%d) $_ => %s\n",
                length $hash{ $_ }, substr $hash{ $_ }, 0, 50;
        }
    }
}

$hash{ $_ } = chr( 64 + $_ ) x $M for 1 .. 25;

my @threads = map{ threads->create( \&process ) } 1 .. 10;

$_->join for @threads;