Tanktalus is most likely right. If you are not sure how often and how much data will be sent to your thread, you should really do something like

use IO::Select;
my $s = IO::Select->new();
$s->add(\*FILE);
my @ready = $s->can_read(1800); # 60*30 seconds = 30 minutes
foreach (@ready)
{
    # read your handle
}
[download]

Updated: Thanks to Tanktalus for pointing out a few typos.