$ cat split.pl

#!/usr/bin/perl

$input = "intranet,monitor(nagios,zabbix,cricket),tacacs(live,test),ldap(dump,prod,domain),test1";

@output = ();

push(@output, $+) while $input =~ m{([^,\(]+\([^\)]+\)),|([^,]+),|,}gx;

print join "\n",@output;
print "\n";

$ ./split.pl
intranet
monitor(nagios,zabbix,cricket)
tacacs(live,test)
ldap(dump,prod,domain)
$