use strict;
use warnings;
use CAM::PDF;

my $infile  = 'input.pdf';
my $outfile = 'output.pdf';
my $pdf     = CAM::PDF->new($infile) or die 'wtf';
my @FIELDS  = $pdf->getFormFieldList();

$pdf->fillFormFields($FIELDS[9] => 'test');
$pdf->cleanoutput($outfile);