phpman > perldoc > truncate(21)

    truncate FILEHANDLE,LENGTH
    truncate EXPR,LENGTH
            Truncates the file opened on FILEHANDLE, or named by EXPR, to
            the specified length. Raises an exception if truncate isn't
            implemented on your system. Returns true if successful, "undef"
            on error.

            The behavior is undefined if LENGTH is greater than the length
            of the file.

            The position in the file of FILEHANDLE is left unchanged. You
            may want to call seek before writing to the file.

            Portability issues: "truncate" in perlport.