I need a function that checks if file exists

Seems to me that (on Windows) we can be assured that the specified $file exists if any one of the following three conditions returns true:

-T $file || -B $file
defined -T $file
defined -B $file
[download]

I was also wondering about using -f instead of -e. Are there any files on Windows that will report false for -f ? (If so, then we can't use -f as a test for existence.)

Someone really ought to file a bug report about this because the perldoc -f -X documentation does *not* match the behaviour wrt '-e'.
That documentation implies that -e '""' will return true only if a file named "" exists.
Either the behaviour ought to change to fit the documentation, or the documentation be amended to fit the behaviour.
The documentation also implies that defined -f '""' will return false (but it doesn't).
Here's what I ran as a check:

#!perl -l
use warnings;

print "-f:";
-f '""'
  ? print "Returned True (unwanted behaviour)\n"
  : print "Returned False (wanted behaviour)\n";

print "defined -f:";        
defined -f '""'
  ? print "Returned True (unwanted behaviour)\n"
  : print "Returned False (wanted behaviour)\n";

print "-T || -B:";
(-T '""' || -B '""')
  ? print "Returned True (unwanted behaviour)\n"
  : print "Returned False (wanted behaviour)\n";

print "defined -T:";
defined -T '""'
  ? print "Returned True (unwanted behaviour)\n"
  : print "Returned False (wanted behaviour)\n";

print "defined -B:";
defined -B '""'
  ? print "Returned True (unwanted behaviour)\n"
  : print "Returned False (wanted behaviour)\n";
[download]

And here's the output I got:

-f:
Returned False (wanted behaviour)

defined -f:
Returned True (unwanted behaviour)

-T || -B:
Returned False (wanted behaviour)

defined -T:
Returned False (wanted behaviour)

defined -B:
Returned False (wanted behaviour)
[download]

I don't mind filing a bug report about this, but I'll wait for comments about that first (in case I've overlooked something).

Cheers,
Rob