@READSCR

@READSCR[row,col,length]:  Returns the text displayed on the screen at the 
specified location.  The upper left corner of the screen is location 0,0. 

The row and column can be specified as an offset from the current cursor 
location by preceding either value with a [+] or [-].  For example, 

        %@readscr[-2,+2,10]

returns 10 characters from the screen, starting 2 rows above and 2 columns 
to the right of the current cursor position. 

You can also specify the row and column as offsets from the current cursor 
position.  Begin the value with a plus sign [+] to read the screen the 
specified number of rows below (or columns to the right of) the current 
position, or with a minus sign [-] to read the screen above (or to the 
left of) the current position.