It would be faster indeed, if it could be applied. Unfortunately, that's not possible because mirc separates the items from the data with LF's, so the saved file looks to /filter like this:
item1
data1
item2
data2
item3
data3
....
Things aren't better if you /hsave with the -b switch either: mirc uses 04 00 and 05 00 to separate items from data.
If only $regsub supported binvars...
