Sorry, this question is way over my head. I got as far as plotting your data but it doesn't look like a bell curve... more like twin peaks. In case it helps as an example of a line graph, here's the script:
#!/usr/bin/perl
#bell_curve_line.pl
use strict;
use warnings;
use GD::Graph::lines;
my $perlscriptsdir = '/home/david/Programming/Perl';
#For some reason, installing GD::Graph didn't put save.pl in my @INC path
require "/usr/share/doc/libgd-graph-perl/examples/samples/save.pl";
my $chart_file_out = 'bell_line';
print STDERR "Processing $chart_file_out\n";
#The @data array is an array of array references
# to an array of x values and an array of y values.
my @data = (
[ qw(1 2 3 4 5 6 7 8 9 10 11 12 13 14 ) ],
[ qw(2 50 40 300 70 80 8 10 25 60 350 80 40 5 )],);
my $my_graph = new GD::Graph::lines();
$my_graph->set(
x_label => 'X',
y_label => 'Frequency?',
title => 'Frequency of Various Values of X',
y_max_value => 350,
y_min_value => 2,
y_tick_number => 10,
y_label_skip => 2,
box_axis => 0,
line_width => 3,
transparent => 0,
);
$my_graph->plot(\@data);
save_chart($my_graph, "$perlscriptsdir/data/$chart_file_out");
Running this creates a file called "bell_line.gif" (see attached).
Unsolved 
