The problem is that you call the param() subs in list context, so they return an empty list (not undef) which then get flattened into "no element".

Assuming you expect max 1 argument per param(), you might try:

my $hash = {
  "file"=>shift(@params),
  "text"=>scalar param("lite"),
  "session"=> scalar param("session")
};
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if you really want to allow more than 1 argument per param(), you could put them in an anonymous array:

my $hash = {
  "file"=>shift(@params),
  "text"=>[ param("lite") ],
  "session"=> [ param("session") ] 
};
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See also:

perldoc perldata
perldoc CGI
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-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.
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