Here's one way; I presented something similar in Fibonacci numbers with lvalues. I give this one as I think it presents an interesting reminder of how "parallel assignment" is useful.

The modification to use Math::BigInt would be easy but obfuscatory for this example.

my ($a,$b)=(1,2);       # Start sequence at 1,2 like in code
print "$a\n$b\n";
for(1..$n-2) {
  ($a,$b) = ($b,$a+$b);
  print "$b\n"
}
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