Sick Unix Trick #347 ... ghost files.

# Open the file, creating it
open $fh, '+>', 'foo.txt';

# Immediately unlink the file ... it will remain
# until you close the filehandle, then disappear
unlink 'foo.txt';

# Put something in it to test
print $fh "Foo\n";

# Rewind to the start of the temp file
seek $fh, 0, 0;

# Read it back in and see what you have
$in = <$fh>;
print "Read: $in\n";

# You don't even *have* to remember to close it,
# but it is a good habit ...
close $fh;
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Updated: Note that unlike File::Temp, this trick will clean up after itself no matter what happens to the process. It does not depend upon DESTROY being invoked.