Shell Programming and Scripting

use strict;
use IO::Socket;
use vars qw($configfile @listen @filter @unknown @nlisten @pingable);

sub test_connect {
        my ($srvproto, $host, $port) = @_;
        # print "$srvproto\t$host\t$port\n";
        # get the port address
        my $iaddr = inet_aton($host);
        if (defined $iaddr) {
                my $paddr = sockaddr_in($port, $iaddr);
                my $proto = getprotobyname($srvproto);
                # create the socket, connect to the port
                socket(MYSOCK, PF_INET, SOCK_STREAM, $proto)|| die "Failed: $!\n";
                connect(MYSOCK, $paddr);
                my $sockstat=$!;
                if ($sockstat eq "") {
                        @listen=(@listen, [$srvproto, $host, $port]);
                        }
                elsif ($sockstat eq "Connection timed out") {
                        @filter=(@filter, [$srvproto, $host, $port]);
                        }
                elsif ($sockstat eq "Connection refused") {
                        @nlisten=(@nlisten, [$srvproto, $host, $port]);
                        }
                elsif ($sockstat eq "Illegal seek") {
                        @listen=(@listen, [$srvproto, $host, $port]);
                        }
                else {
                        print $sockstat . "\n";
                        }
                close MYSOCK or die "close: $!";
        } else {
                @unknown=(@unknown, [$srvproto, $host, $port]);
        }
}

               In the second form, the code within the BLOCK is parsed only
               once--at the same time the code surrounding the "eval" itself
               was parsed--and executed within the context of the current Perl
               program.  This form is typically used to trap exceptions more
               efficiently than the first (see below), while also providing
               the benefit of checking the code within BLOCK at compile time

-- excerpt from perldoc -f eval