OK, I tested this with v5.8.0 built for i386-linux-thread-multi.

Test data was a 32M, 2.5 million line file.
Machine is a 1740Mhz Althon, 512Mb real memory, 768Mb swap.

Results:

my_slurp:

Try 1
Took 11 seconds.
Try 2
Took 16 seconds.
Try 3
Took 15 seconds.

my_while:

Try 1
Took 4 seconds.
Try 2
Took 5 seconds.
Try 3
Took 4 seconds.

my_file:

Try 1
Took 33 seconds.
Try 2
Took 19 seconds.
Try 3
Took 14 seconds.
[download]

---

If the information in this post is inaccurate, or just plain wrong, don't just downvote - please post explaining what's wrong.
That way everyone learns.