[Templates] Vmethods to add to 2.15

[Josh Rosenbaum]

Sergey Martynoff wrote:
> But what about support for backslash-escaped '$' sign in replace
> string? It seems to be achieved quite easily, changind the line
> where actual replace takes place:
> 
>>                 $matched =~ s/\$$i/$backref/g;
> 
> with this:
> 
>     $matched =~ s/(?<!\\)\$$i(?!\d)/$backref/g;
> 
> This also solves probles with "unused" backreferences, when you
> use something like replace("(this)","that$10") ending up with
> "that0" instead of desired "that".


I saw this in Paul's code as well. I think it's a pretty good idea, 
but there is one thing to point out. It gives the user the impression 
that escaping is valid in replacement.

For example if the string is '\\$3' what then? Do we escape the 
backslash.  This could be a slippery slope, but for now I'm fine with 
saying '\$' and '\\$' are both invalid for backrefs for now.

Given that '$' is used quite a bit for money, I think it's probably a 
good thing to allow escaping.

-- Josh