Perhaps you can adapt this.

# perl
use strict;
use GD::3DBarGrapher qw(creategraph);
use GD;
use HTML::Treebuilder;
use Data::Dump 'pp';

my @data = (
    ['Apples', 28],
    ['Pears',  43],
    ['Bananas',67],
);
 
my %options = (
  'file' => 'mygraph.jpg',
);

my $imagemap = creategraph(\@data, \%options);

my $tree = HTML::TreeBuilder->new; 
$tree->parse($imagemap);
my @elements = $tree->find_by_tag_name('area');
my %plot=();
for my $e (@elements){
  my ($bar,$value) = split ':',$e->attr('title');
  $plot{$bar}{'value'} = $value;
  my @coord = split ',',$e->attr('coords');
  $plot{$bar}{'coord'} = \@coord;
}
#pp %plot;

my $img = GD::Image->newFromJpeg('mygraph.jpg',[1]);
my $black = $img->colorAllocate(0,0,0);      
for my $bar (keys %plot){
  my $x = $plot{$bar}{'coord'}[0];
  my $y = $plot{$bar}{'coord'}[1] - 20; # above bar
  my $v = $plot{$bar}{'value'};
  # gdSmallFont, gdMediumBoldFont, gdTinyFont, 
  # gdLargeFont and gdGiantFont.
  $img->string(gdMediumBoldFont,$x,$y,$v,$black);
}
open IMG,'>mygraph.png';
binmode IMG;
print IMG $img->png;
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        else {
            # draw main bar face
            my $centretopy = $ypos + ($dims{plotheight} - (($dims{plot
+height}/$dims{range})*$d->[1])) + $floordepth;
            $image->filledRectangle($barpos,$centretopy,$barpos+$conf{
+bwidth},$ypos+$dims{plotheight}+$floordepth,$colbar);
### add this line
      $image->string(gdSmallFont,$barpos,$centretopy-20,$d->[1],$colba
+r);
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