ruby for array

a=1
for a in 1..3
  print a;
end  

str="hello";
if $str ="hello"
 print $str;
end
array=[2,4,4,3,4];
print array.to_s+"\n";
print array.pop; #4

a="hello";
a << "world";
a.concat(33);
print a; #helloworld 不懂什么意思。