my @examples=(
    'KG 001 J',
    'KG 003 M',
    'KG 004 A',
    'KG 007 X',
    'KG 020 M',
    'KG 045 A',
    'KG 1234 J',
  );

for my $string (@examples)
{
  if($string=~/KG\s(\d{3})\s([JMA])/)
  {
    my ($number,$suffix)=($1+0,$2);
    print "$string => ";
    print "NUMBER: $number ";
    print "SUFFIX: $suffix\n";
  }
}