#!/usr/bin/perl -w
use strict;
use warnings;

my @E1 = (2, 3.23, 7, 9, 11.3479);
my @E2 = (3.3333, 1.433, 8.0577, 9.7344, 13.3377);

my ($Alow, $Ahi, $Astep) =
#       (.5, 5, .1);
#       (0.8, 1.0, 0.025);
#       (0.85, 0.9, 0.005);
        (0.87, 0.88, 0.001);

for (my $A=$Alow; $A <= $Ahi; $A+=$Astep) {
        printf "%7.4f %5.3f\n", $A, current_error($A);
}

sub current_error {
        my $A = shift;
        my $err=0;
        for (my $i=0; $i<@E1; ++$i) {
                my $t = $E1[$i] - $A*$E2[$i];
                $err += $t*$t;
        }
        return $err;
}

##</code><code>##

Roboticus@Roboticus-PC ~
$ ./curvefit.pl
 0.8700 5.091
 0.8710 5.088
 0.8720 5.086
 0.8730 5.085
 0.8740 5.084
 0.8750 5.085
 0.8760 5.085
 0.8770 5.087
 0.8780 5.089
 0.8790 5.092
 0.8800 5.096