I hope I get a merit badge for this. :-) This will take the current amount on the commandline and generate the thermometer. It could use some enhancements, but it should get you started.

#!/usr/bin/perl 
use warnings;
use strict;
use GD;
use GD::Text::Align;

my $current = shift;
$current ||= 500;

my $goal = 10000;

my $image = new GD::Image(250,500);

my $black = $image->colorAllocate(0,0,0);
my $white = $image->colorAllocate(255,255,255);
my $red = $image->colorAllocate(255,0,0);

my $top = 20;
my $bottom = 400;
my $dif = $bottom - $top;
my $left_text_margin = 65;

#background, set tranparent if you want
$image->filledRectangle( 0, 0, 250, 500, $white );
#$image->rectangle($x1,$y1,$x2,$y2,$color)
$image->rectangle(40,20,60,425,$black);
#$image->filledEllipse($cx,$cy,$width,$height,$color)
$image->filledEllipse(50,450,75,75,$red);

$image->filledRectangle(40,400,60,425,$red);


my $text = new GD::Text::Align( $image,
         font => gdLargeFont,
#         font => './arial.ttf',
         text => $goal.' Our Goal',
         color =>  $black,
         valign => "center",
         halign => "left",
);

#draw goal at top
$text->draw($left_text_margin,$top);

#draw start at bottom
$text->set_text('0 Start');
$text->draw($left_text_margin,$bottom);

show_current();

open( IMAGE, ">GD-thermometer.png") || die "Couldn't open file: $!\n";
binmode( IMAGE );
print IMAGE $image->png();
close IMAGE;


sub show_current{

my $curpix = 400 - ($dif/$goal)* $current;  

#draw text level
$text->set_text("$current Current");
$text->draw($left_text_margin,$curpix);
  
$image->filledRectangle(40,$curpix ,60,425,$red);

}
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