Check the man page for 'pcap'. It specifies that the 'timeout' should not be relied upon as it is not supported on all platforms.

To get around this and capture with a timeout, I've done the following with some success:

use Net::Pcap;

my $device = ...
my $snaplen = ...
my $timeout = ... * 1000 # in milliseconds * 1000 = seconds
my $err;

my $pcaprecv = Net::Pcap::pcap_open_live($device, $snaplen, 1, $timeou
+t, \$err);

my $recv_r;
my %header;
my $starttime = time;
while (1) {
    my $ret = Net::Pcap::pcap_next_ex($pcaprecv, \%header, \$recv_r);
    if ($ret == 1) {
        # Found packet - do stuff
    } elsif ($ret == 0) {
        print "[Receive Timeout] ";
        last
    } else {
        print "[Receive Error] ";
        last
    }
    if ((time - $starttime) >= $timeout) {
        print "[Receive Timeout] ";
        last
    }
}
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