Perhaps something like this ..

my @a;
for(0..3){
   $a[$_]=[$_*5+1..$_*5+5]; 
   print qq(a[$_]= @{$a[$_]}\n);
}
--Output--
a[0]= 1 2 3 4 5
a[1]= 6 7 8 9 10
a[2]= 11 12 13 14 15
a[3]= 16 17 18 19 20
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