my @x = (0,1); #pretend we had 0 and 1 already
print "@x ";    #first fibonaccis

for (my $counter = 2;$counter < 20;$counter++) {
    my $newVal = $x[-1] + $x[-2];
    print "$newVal ";
    push(@x,$newVal);
    shift(@x);        #remove the old first value from the list
}