my $formula = 'c + a * x^2';

##</code><code>##

$ perl -MO=Deparse,-p -e 'my $formula = $c + $a * $x**2;'
(my $formula = ($c + ($a * ($x ** 2))));
-e syntax OK

##</code><code>##

$ perl -MO=Deparse,-p -e 'my $formula = $c + $a * $x^2;'
(my $formula = (($c + ($a * $x)) ^ 2));
-e syntax OK