@h0, @h1, @h2, ... @h4 - History Group Variables.
Each history buffer contains 20 slots which contain the history information. The history slot is selected with the index argument which is valid in the range 0..19, index 0 is the most recent history slot in the history group.
The history slots are automatically modified on the entry of a new command, search string etc.
@hn index returns the whole of the history string for a given slot.
An error is generated if an attempt is made to access these variables and history buffer identifier n or the index is out of range.
@hn was first introduced in the January 2004 release.