installed the pdftk binary file and the path to variable and tried running , getting error as below: Error: "pdftk input.pdf owner_pw foopass outPDF.pdf failed: -1 at /usr/lib/perl5/site_perl/5.10.0/PDF/Tk.pm line 73."

use PDF::Tk;
my $doc=PDF::Tk->new(pdftk=>'/apps/free/pdftk/');
$doc->call_pdftk('input.pdf', 'outPDF.pdf', 'owner_pw', 'foopass');
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please guide me in resolving it