Macro for Backslash Substitution

[ephemeric]

I have a macro that adds a backslash to an existing backslash:

[backslash(1)]
args = arg
definition = replace("$arg$", "(\\\\)", "\\\\\\\\")
iseval = 1

 This works:

index=perfmon counter=`backslash(\processor)`

 This fails when the arg has spaces:

index=perfmon counter=`backslash("\processor time")`

The expanded search string:

(counter=\\processor index=perfmon time)

How do I get:

index=perfmon counter="\\processor time"

Oh please show me my stupidity as I have been banging my head on the desk for hours...