EXIT SELECT transfers execution past the matching END SELECT statement, bypassing any CASE ELSE or CASE ALL statements.

NEXT CASE transfers execution directly to the next CASE statement where execution continues as if no CASE statement had matched.  NEXT CASE transfers execution to the next CASE statement, not into the block, so the next CASE block and subsequent CASE blocks are executed only if one of its case-expressions matches the test expressions.

XBasic does not support an ELSEIF statement because SELECT CASE TRUE is equivalent, more flexible, better structured, easier to read, more compact, and faster.