PROCEDURE INSERT((* pattern *)	     SSTRN: MSTRING;
		 (*  dest   *) VAR DESSTRN: DSTRING;
		 (* position*)	     POSN : integer);
{++++++++++++++++++++++++++++++++++++++++++++++}
{+  inserts the string SSTRN into the string  +}
{+  DESSTRN at position POSN.		      +}
{++++++++++++++++++++++++++++++++++++++++++++++}
VAR	rpart: MSTRING;
BEGIN
  If ( length(DESSTRN)+length(SSTRN) <= DEFAULT ) then
    begin { seperate destination string into left and right parts. }
      { first extract the right part. }
      rpart := COPY(DESSTRN,POSN,(length(DESSTRN)-POSN+1));
      { next take left part of DESSTRN. }
      setlength(DESSTRN,(POSN-1));
      { new := left + substring + right }
      append(DESSTRN,SSTRN);
      append(DESSTRN, rpart);
    end;
{ else do nothing. leave DESSTRN as it was. }
END; { of INSERT }
d(DESSTRN,SSTRN);
      append(DESSTRN, rpart);
    e