[1] 
[PRE(example code)[
Plural-Forms: nplurals=2; plural=(n != 1);
]PRE]

[2]
[PRE(example code)[
Plural-Forms: nplurals=2; plural=n != 1;
]PRE]

[3]
[PRE(example code)[
Plural-Forms: nplurals=1; plural=0; 
]PRE]

[4]
[PRE(example code)[
Plural-Forms: nplurals=2; plural=(n==1?0:1);
]PRE]