#! /usr/bin/perl -w
use strict;
use threads;

sub calculation {
    print("calculating something\n");
    5;
}

# Starting a co-process to read from.
my $procid = open(
    READ, '-|',
    'perl -e "$|=1; for (1..10) {print \"Line $_\n\"; sleep 1;}"'
);

##switch the order of the previous and next lines and the crash does not occur.
my $thread = async(\&calculation);

# Reading from co-process.
until ( 0 ) {
    my $line = <READ>;
    last unless defined $line;
    print $line;
}

close(READ);

print $thread->join() ."\n";