The function passed to alarm_call is not called on timeout as you expect. The function passed to alarm_call is the one alarm_call will interupt after the specified timeout. Reread the docs.

sub socket_read {
    my $len;

    {
        ($len, my $errmsg) = alarm_call(60, '->sysread', $socket, $lin
+e, 1024);

        if (defined($len)) {
            if ($len eq 'TIMEOUT') {
               print STDERR "Received alarm\n";
               redo;
            }

            if ($len eq 'ERROR') {
               die($errmsg);
            }
        }
    }

    ...
}
[download]

Of course, you could also use alarm directly.

sub socket_read {
    my $len;

    {
        eval {
            local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n require
+d
            alarm 60;
            $len = $socket->sysread($line, 1024);
        };
        alarm 0;

        if (my $e = $@) {
            if ($e eq "alarm\n") {
               print STDERR "Received alarm\n";
               redo;
            }

            die($e);
        }
    }

    ...
}
[download]

Untested.

Update: Added second snippet. Handle exceptions.