I'm trying to compare 2 variables in a condition, something like

<condition field="${sip_from_user}" expression="^${some_other_phone_number}$" inline="true">

But it looks like FS expands the variable, and does the comparison. The problem with this is, those 2 phone numbers are in e.164, i.e.:

sip_from_user = +18885551212

some_other_phone_number = +18005551212

and so the condition ends up being:

<condition field="+18885551212" expression="^+18005551212$" inline="true">

which of course won't work....

Is there any way of escaping the variables automatically when comparing?

I haven't found a way.