fn:starts-with

fn:starts-with(
   $parameter1 as xs:string?,
   $parameter2 as xs:string?,
   [$collation as xs:string]
) as xs:boolean

Returns true if the first parameter starts with the string from the second parameter, otherwise returns false.

Parameters
parameter1	The string from which to test.
parameter2	The string to test whether it is at the beginning of the first parameter.
collation	The optional name of a valid collation URI. For information on the collation URI syntax, see the Search Developer's Guide.

fn:starts-with("abcd", "ab")

=> true