Here's the flat boneheaded way; get them as strings,

$ perl -e'for (1..10) { printf "%04d", int rand 10000 for 1..3; print 
+$/ }'
514418728718
307337438051
439351593615
060710058137
425610029405
005219485294
477480663085
055060660839
412479203930
462907707151
$
[download]

You can use sprintf and concatenation if you want them in memory. That's not entirely dumb; you can initialize Math::BigInts with them.

Test these, too. PRNG's often show periodicity in the low bits, and left-shifting them is asking for trouble.