in reply to How can I enter the data of different variables from a text file into a perl program?
I happen to have written a module which understands that syntax. You could use it like this:
my $m = Math::Expression::Evaluator->new;
# read all the variables
$m->parse("x1=3.8; x2=5.8; x3=4.1; y1=10.1; y2=11.6; y3=12.7")->val;
# do the calculations you are interested in:
say $m->parse("x1 * x2")->val;
Not saying it's the best solution, it just happens to work :-)