As ever, the help is your friend:
elp?> ;
search: ;
;
; has a similar role in Julia as in many C-like languages, and is used to delimit the end of the previous statement.
; is not necessary at the end of a line, but can be used to separate statements on a single line or to join statements into a single expression.
Adding ; at the end of a line in the REPL will suppress printing the result of that expression.
In function declarations, and optionally in calls, ; separates regular arguments from keywords.
In array literals, arguments separated by semicolons have their contents concatenated together. A separator made of a single ; concatenates vertically (i.e. along the first dimension), ;; concatenates horizontally (second dimension),
;;; concatenates along the third dimension, etc. Such a separator can also be used in last position in the square brackets to add trailing dimensions of length 1.
A ; in first position inside of parentheses can be used to construct a named tuple. The same (; ...) syntax on the left side of an assignment allows for property destructuring.
In the standard REPL, typing ; on an empty line will switch to shell mode.
(second to last paragraph)