If they are going to the trouble of installing your script on multiple machines, then you can just add the module in with your tarball and build your requires such that your script uses a local copy of the module rather than using the machine-wide modules. Other solutions would include cutting and pasting the necessary subs from the module to your script.

As to the original question, you haven't said whether this is just splitting the data into two columns ( 1, 2; 3, 4; 5, 6; ) as you go over it or whether you want to go down the first column, then wrap to the second (1, 4; 2, 5; 3, 6 ).

In the first case, you might consider a while loop using shift (make sure to copy the list, since shift will destroy it). In the second case, you need to split the list into two parts, then you can loop over the two half-lists by index.