Binary data versus numbers:

print "\x45" | "\x59"; # Prints \x5d.
print 'E'    | 'Y';    # Same as the above, prints ].
print 69     | 89;     # Prints 93 (5d in hex).
[download]

| is clever, it knows whether it operates on bytes (strings) or numbers.

Update: fixed typo (s/78/89/), thanks poj.