Actually, the server that doesn't work was using Tie:File 0.95, whereas my local machine is using 0.93 (as well as Perl 5.6.1, just like the server)

I uninstalled 0.95 and reinstalled w/ 0.93 just to see, same dice.

I've made the change you suggested, and unfortunately dumb luck isn't with me. See below for the results. (the file.txt file starts out with 7 identical lines, and ends as you see)

bash-2.05a$ vi tie
bash-2.05a$ ./tie
Use of uninitialized value in read at /usr/lib/perl5/5.6.1/Tie/File.pm
+ line 699, <FH> line 7.
Use of uninitialized value in read at /usr/lib/perl5/5.6.1/Tie/File.pm
+ line 699, <FH> line 7.
bash-2.05a$ cat file.txt
this is a really long line of text (sortof)
 TestText
TestText TestText TestText
TestText TestText TestText
TestText TestText TestText
TestText TestText TestText
TestText TestText TestText
bash-2.05a$
[download]

Note the complaints about line 699 of File.pm.....