All you need to do is build a hash of keys/values, create a user agent with 
the  
LWP library, and then post a hash reference to Iongate:  
 
#!/usr/bin/perl -w  
 
use strict; 
use HTTP::Request::Common qw(POST); 
use LWP::UserAgent; 
$|=1;  
 
my %params = ();  
 
$params{'LOGIN'} = 'testgate'; 
$params{'AMOUNT'} = '15.00'; 
$aprams{'CARDTYPE'} = 'VISA'; 
$params{'CARDNUM'} = '4111111111111111'; 
$params{'EXPIRES'} = '1203';  
 
... [etc.]  
 
my $userAgent = new LWP::UserAgent;  
 
my $res = $userAgent->request( 
POST 'https://secure.iongate.com/iongate.asp', 
\%params 
);  
 
if ($res->is_success) { 
my $returned_content = $res->content; 
... [process returned content here] 
} 
[etc.]

#!/usr/bin/perl -w 
 
use strict; 
use CGI; 
use HTTP::Request::Common qw(POST); 
use CGI::Carp qw/fatalsToBrowser/; 
use LWP::UserAgent; 
$|=1; 
 
my %params = (); 
 
$params{'LOGIN'} = 'testgate'; 
$params{'AMOUNT'} = '15.00'; 
$params{'CARDTYPE'} = 'VISA'; 
$params{'CARDNUM'} = '4111111111111111'; 
$params{'EXPIRES'} = '1203'; 
 
my $userAgent = new LWP::UserAgent; 
 
my $res = $userAgent->request( 
POST 'https://secure.iongate.com/iongate.asp', 
\%params 
); 
 
if ($res->is_success) { 
my $returned_content = $res->content; 
print "It worked"; 
} else { 
print "It didn't work"; 
}