use subs 'open';
sub open {
  my $params = scalar @_;
  print "received $params parameters...\n";
  my $filehandle = shift;
  print "received filehandle $filehandle...\n";
  print "received list @_[0..$#_]...\n";
  my $return;
  $return = CORE::open($filehandle,@_[0..$#_]);
  return $return;
}
my $result;
$result = open(TEST);
print $result,$/;
close(TEST);
$result = open(TEST, "test.txt");
print $result,$/;
close(TEST);
$result = open(TEST, "<test.txt");
print $result,$/;
close(TEST);
$result = open(TEST, "<", "test.txt");
print $result,$/;
close(TEST);
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Did I miss something (upd.: yes, I did) or couldn't this be cut down to simply:

use subs 'open';
sub open {
    print @_ . "parameters: @_\n";
    CORE::open(@_[0..$#_]);
}
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(I didn't test anything, so I may well be way off the mark.)

Makeshifts last the longest.

No, it can't. The CORE::open does not succeed if you do not hand it a scalar filehandle.

use subs 'open';
sub open {
  print @_ . " parameters: @_\n";
  my $filehandle = shift;
  CORE::open($filehandle,@_[0..$#_]);
}
sub open2 {
    print @_ . " parameters: @_\n";
    CORE::open(@_[0..$#_]);
}

my $result;

print "Testing open...\n";
print open(TEST),$/;
print open(TEST, "test.txt"),$/;
print open(TEST, "<test.txt"),$/;
print open(TEST, "<", "test.txt"),$/;
print $/;
print "Testing open2...\n";
print open2(TEST),$/;
print open2(TEST, "test.txt"),$/;
print open2(TEST, "<test.txt"),$/;
print open2(TEST, "<", "test.txt"),$/;
print $/;
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I figured that I would update this for the benefit of anyone who comes along and decides to try it. I went with Mr. Muskrat's idea and it has worked great. Recently I had a problem handling a first arg that is an undefined scalar, for example:

open(my $file, "<", $file);
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Again tilly came to the rescue: see anonymous filehandle for overridden open sub.

-Joe