2.17 Swap 2 columns in a matrix

Give a matrix

     1     2 
     3     4 
     5     6
 

How to change it so that the second column becomes the first, and the first becomes the second? so that the result become

     2     1 
     4     3 
     6     5
 

Mathematica a={{1,2}, {3,4}, {5,6}} Reverse[a,2]

Out[29]= {{2, 1}, {4, 3}, {6, 5}}

 

Matlab a =[1 2; 3 4; 5 6] [a(:,2) a(:,1)]

2 1 4 3 6 5

 

Maple A:=Matrix([[1,2],[3,4],[5,6]]); A:=Matrix([ A[..,2], A[..,1] ])

[[2,1], [4,3], [6,5]]