I think you must have  <form ... enctype="multipart/form-data"> in the HTML form in order to make the client's user agent encode the form, including the file's contents, in the multipart/form-data encoding. And then CGI.pm will help parsing it.

use CGI;
my $q=new CGI;
my $file=$q->param('foo'); #foo is the name of the file field in the f
+orm
print "You uploaded $file:"; #$file is the name of the file
print <$file>; #and it can also be used as a file handle to get the co
+ntents of the file
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