Isdbref()
isdbref(<string>)
This function will return 1 if the string passed to it is a valid dbref. To be a valid dbref the string must begin with '#' and be followed by an integer. Also, the dbref must exist in the current database as a valid object. If the object fails either of these criteria, then a 0 is returned.
Examples
> say isdbref(#-1)
You say "0"
> say isdbref(#1)
You say "1"
> say isdbref(This is not a dbref)
You say "0"