blogger layout syntax question

Question

I know this

on the javascript programming

if(a==b){}else{}

same code on the blogger blog template syntax

<b:if cond='a==b'>
<b:else/>
</b:if>

I need, how to do following on the blogger

1. if(a==b) || (c==a) how to create multi conditional expression ?
2. data:blog.url.substring(40) how to subtract data:blog.url string. ?
3. data:blog.url.indexOf("label") how to search from data:blog.url string ?