$a=3;
$b="x";
$c=4;
$a*=3; #$a=$a*3; $a now equal to 9;
$a/=3; #$a=$a/3; $a (9) divided by three which equals 3;
$a+=2; #$a=$a+2; $a is now equal to 5;
$a-=2; #$a=$a-2; $a is now equal to 3;
$b x=3; #$b=$b x $3 $b is now equal to "xxx";
$b .="33"; #b=$b."33" $b is now equal to "xxx33";