sub dbconnect {
    socket(my $mysocket, PF_INET, SOCK_STREAM, getprotobyname('tcp'))
        or die("socket: $!");

    fileno($mysocket) >= 100
        or die("No available file descriptors below 100\n");

    # ...
}

##</code><code>##

use strict;
use warnings;

use Socket;

my @handles;
for (0..9) {
    open($handles[$_], '<', $0) or die;
    print("$_: ", fileno($handles[$_]), "\n");
}

print("--\n");

close($handles[5]);

socket(my $mysocket, PF_INET, SOCK_STREAM, getprotobyname('tcp')) or die;
print(fileno($mysocket), "\n");

##</code><code>##

0: 3
1: 4
2: 6
3: 8
4: 9
5: 10
6: 11
7: 12
8: 13
9: 14
--
10