You are not checking for an empty value, you are setting one. And if you don't do that, you are setting it to undef which is just as bad. Here is what I think you should be doing:

my $got_file_name = $cgi->param( 'doc_upload' );

# Store file name to use later but only if it is defined.
$session->param("doc_uploaded", $got_file_name) if $got_file_name;
my $filename_uploaded = $session->param("doc_uploaded");

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In reply to Re^3: Losing session value by hippo
in thread Lossing session value by Anonymous Monk

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