How? Filter = All tiddlers with prefix of currentTiddler

ARGH! Why doesn’t this work? I want all the tiddlers that start with the title of the current tiddler but not including the current tiddler. One would think this would work.

<<tabs "[!is[system]prefix[<currentTiddler>]sort[caption]] -[is[current]]" "" "$:/state/tab1" "tc-vertical">>

There is an extra set of square brackets around the variable currentTiddler that are not needed.
<<tabs "[!is[system]prefix<currentTiddler>sort[caption]] -[<currentTiddler>]" "" "$:/state/tab1" "tc-vertical">>

Thanks a bunch, Saq!