The select_region_point operator can be used to obtain a complete region through a point within a region or part of a region.

If you know a point within a region, get the full region that contains the point, instance:

Connection (Wordreg, regions) while
(1)
    Get_mbutton (Windowhandle,row,col,button)
    Select_region_point ( Regions, Targinregion, Row, Col)
    dev_display (Image)
    dev_set_draw (' Fill ')
    dev_set_color (' Green '
    ) Dev_display (targinregion)
    stop ()
Endwhile

If you know a part of a zone, you can do so by getting the area outline and then getting the first point:

while (1)
    draw_rectangle1 (WindowHandle, Row1, Col1, Row2, Col2)
    gen_rectangle1 (Rectangle, Row1, Col1, Row2, Col2)
    get_region_contour (Rectangle, rows, Cols)
    tuple_length (rows, L)
    if (L > 0)
        tuple_select (Rows, 0, Row)
        Tuple_select (Cols, 0, Col)
    endif
    Connection (Wordreg, regions)
    Select_region_point (regions, Targinregion, Row, Col)
    dev_display (Image)
    dev_set_draw (' Fill ')
    dev_set_color (' green ')
    dev_ Display (targinregion)
    stop ()
Endwhile