print $_,  
    ((not $_ % 4 xor $_ % 100 xor $_ % 400) 
    ? ' is ' 
    : ' is not ', 
    'a leap year'), $/ 
    for 1996, 1997, 1998, 1999, 2000, 2004, 2100;

1996  is  a leap year
1997  is not  a leap year
1998  is not  a leap year
1999  is not  a leap year
2000  is  a leap year
2004  is  a leap year
2100  is not  a leap year