Non-functional case

program Project2;
{$APPTYPE CONSOLE}
{$R *.res}
uses
  System.SysUtils;

const
   Amount = 5;
   ErrorMessage = 'Error! Enter name (nonempty string, starts with uppercase letter)';
function IsName(Name: string) : Boolean;
var
   NameLength, i : Integer;
   HasSuchLetter : Boolean;
   Alphabet : set of 'a'..'z';
begin
   Alphabet := ['a'..'z'];
   NameLength := Length(Name);
   IsName := True;

   if Name <> '' then
      if Name[1] <> LowerCase(Name[1]) then
         for i := 2 to NameLength do
            if not (Name[i] in Alphabet) then
               IsName := False
      else
         IsName := False
   else
      IsName := False;
end;

var
   MyName : string;
   i, Counter, Index : Integer;
   HasStarted, IsInvalid : Boolean;
   List: array [0 .. 4] of string = ('Artem', 'Maxim', 'Arseniy', 'Vasya', 'Merlin');

begin
   HasStarted := False;
   IsInvalid := True;
   Writeln('This program can recognize and greet one of 5 friends');
   repeat
      Counter := 0;
      Index := -1;
      while IsInvalid do
         try
            if not HasStarted then
               Writeln('Enter name:')
            else
               Writeln('Please, clarify the name:');
            Readln(MyName);
            if (MyName = '') or (MyName[1] = LowerCase(MyName[1])) then
               Writeln(ErrorMessage)
            else
               IsInvalid := False;
         except
            Writeln(ErrorMessage);
         end;
      IsInvalid := True;
      for i := 0 to Amount - 1 do
         if Pos(MyName, List[i]) = 1 then
         begin
            Counter := Counter + 1;
            Index := i;
         end;
      Writeln('Matches found: ', Counter);
      if Counter = 0 then
         Counter := 1;
      HasStarted := True;
   until Counter = 1;
   if Index = -1 then
      Writeln('I DON''T KNOW YOU!')
   else
      Writeln(List[Index], ', nice to meet you!');
   Readln;
end.