Изменение порядка слов в строке (программа Паскаль)

program REVERSE;
var OLD_LINE, NEW_LINE: string [50];
PROBEL: integer; WORD: string [50];
begin
NEW_LINE := ''; readln (OLD_LINE);
OLD_LINE := concat (OLD_LINE,' ');
while OLD_LINE <> '' do
begin
PROBEL := pos (' ', OLD_LINE);
word := copy (OLD_LINE, 1, PROBEL);
NEW_LINE := concat (WORD, NEW_LINE);
Delete (OLD_LINE, 1, PROBEL);
end;
writeln (NEW_LINE)
end.