HTTP redirect

Did you try something like this:

when HTTP_REQUEST {
if { ([HTTP::host] eq "qat.coworks.bns") and ([HTTP::uri] eq "/") } {
HTTP::respond 301 Location "https://wam.uat.coworks.bns/opensso/UI/Login?realm=bns&module=LDAP&goto=https%3A%2F%2Fwam.uat.coworks.bns%2Fopensso%2FfederationService.jsp%3Fsp%3Dhttps%3A%2F%2Fxcore3.fgvms.com%2FSSOLogin%3FSSOParams%3Dcompany%253DBNS%253B%253Breturningurl%253DcloseWindow%26relayStateURL%3Dcompany%3DBNS%3B%3Breturningurl%3DcloseWindow"
}
}

Personally I would go for policies rather than iRule in this case if you consider perfomance of your BigIP. Nevertheless both will work :

https://support.f5.com/kb/en-us/solutions/public/15000/000/sol15085.html

PS. Policies were introduced at 11.4 so you need to have this one at least.