Hi. First, use strict and warnings and see what happens, then never turn them off again.

Second, don't use "a" or "b" as variable names. They are special.

For your stated objective:

my @cat=(1,2,3);
my @dog=(5,6);
my @pig=(4,3,2,1);

for(\@cat,\@dog,\@pig){
    stuff($_); # stuff() gets an arrayref and will need to dereference
+ it
}
[download]

Hope this helps!