#! perl -slw
use strict;
use threads stack_size => 4096;
use threads::shared;

sub timedCommand {
    my( $timeout, $cmd, @args ) = @_;

    my $pid :shared;
    my @input :shared;

    async {
#        local $_; ### LINE C ###
        $pid = open my $fh, "$cmd @args |" or die "$!, $^E";
        push @input, $_ while <$fh>;
    }->detach;
    sleep 1 until $pid;
    sleep 1 while kill 0, $pid and $timeout--;
    kill 3, $pid if $timeout;

    print "@input"; ### LINE A ###
    return @input;
}

my $cmd = q[ perl -E"$|++; sleep(1), say for 1 .. $ARGV[0]" ];

print timedCommand( 3, $cmd, $_ ) for 2, 3, 4; ### LINE B ###
__END__
C:\test>\perl64-16\bin\perl.exe timedCommand.pl
Thread 1 terminated abnormally: Modification of a read-only value attempted at timedCommand.pl line 15.


Thread 2 terminated abnormally: Modification of a read-only value attempted at timedCommand.pl line 15.