#!/usr/bin/perl -wT

use CGI; my $q = new CGI;

#...

my ( $user_id, $name ) = identify ( $auth_token );

# ...

my $fh = $q->upload( "file" );
my $filesize = -s $fh;
die $filesize; # undef at debugging!
# ... file read routines, that resulted blank after the upgrade

##</code><code>##

sub identify {
   my $token = shift;

   # my $q = new CGI; # it started working when I removed this line!

   # identification routines

   # some calls to CGI.pm methods, where I used $q
}

##</code><code>##

sub identify {
   my $token = shift;
   my $q = shift; # and including this element on the sub call, of course

   my $q = new CGI; # it started working when I removed this line!

   # identification routines

   # some calls to CGI.pm methods, where I used $q
}