in

Returns True if expression is a key in the dynamic array. Can't be used with a static array otherwise it will result in an error.

Syntax:
expression In array[]
expression is the keyword to find in array array[]

Example:
-- Check if key is an index in array a[]
dim a[]
a[1]="one"
a[2]="two"
a[3]="three"
keyword="3"
if keyword in a[] then
    Print keyword; " is a valid index in a[]"
End If