TMSH How to add a irule to a vip with existing irules

That would be fairly easy to do with iControl rest. Something like (using perl):

!/usr/bin/perl

use JSON qw( decode_json );
use Getopt::Std;
%opts=();
getopts("b:rv:tl:",\%opts);

sub Usage {
        print "Usage: $0 [-b ] [-l ] [-r] [-v virtual] [t]\n";
        print "\t -b      target a particular node (default targets the active member of each cluster) \n";
        print "\t -l  : separated rule list\n";
        print "\t -r               replace rather than add\n";
        print "\t -v      virtual to operate on, default is all\n";
        print "\t -t               Test run\n";
        exit;
}

if ($opts{h} || (!keys %opts)) {
        Usage();
}


print "F5 Admin password:";
system('/usr/bin/stty', '-echo');   Disable echoing
my $pass = <>;
system('/usr/bin/stty', 'echo');
chomp $pass;
print "\n";
my $res = `curl -sk -u admin:$pass -H "Content-Type: application/json" -X GET  https://$opts{b}/mgmt/tm/ltm/virtual`;
$decoded = decode_json($res);
foreach my $item ( @{$decoded->{'items'}}) {
        my $json = "{\"name\":\"$item->{'name'}\",\"rules\":[ ";
        if ($opts{v} ) {
          if ( ! ($item->{'name'} =~ /$opts{v}/) )  {
                next;
          }
        }
        if ( $opts{r} || !(exists($item->{'rules'}))) {
                   foreach my $rule (split(/:/,$opts{l})) {
                        $json .= "\"$rule\",";
                   }
                   chop $json;
                   $json .= "] }";
        } elsif (exists($item->{'rules'})) {
                   foreach my $rule ( @{$item->{'rules'}} ) {
                        $json .= "\"$rule\",";
                   }
                   foreach my $rule (split(/:/,$opts{l})) {
                        $json .= "\"$rule\",";
                   }
                   chop $json;
                   $json .= "] }";
        }
        if ($opts{t}) {
                print "curl -sk -u admin:$pass -H \"Content-Type: application/json\" -X PATCH  https://$opts{b}/mgmt/tm/ltm/virtual/$item->{'name'} -d '$json'\n";
        } else {
                `curl -sk -u admin:$pass -H "Content-Type: application/json" -X PATCH  https://$opts{b}/mgmt/tm/ltm/virtual/$item->{'name'} -d $json`;
        }

}