Geez. You are using "Terminal.app", right? What font are you using? I use Monaco, and I see the £ symbol just fine. In case it helps, here are what I guess would be the relevant shell environment variables -- if you type "env" as a command, you should see similar things (I don't actually know what TERM_PROGRAM_VERSION and __CF_USER_TEXT_ENCODING are about):

$ env
TERM_PROGRAM=Apple_Terminal
TERM=xterm-color
SHELL=/bin/bash
TERM_PROGRAM_VERSION=133
__CF_USER_TEXT_ENCODING=0x3B28:0:0
...

$ perl -v

This is perl, v5.8.6 built for darwin-thread-multi-2level
(with 3 registered patches, see perl -V for more detail)
...

$ perl -e 'binmode STDOUT,":utf8"; print "sign: \xa3\n"'              
sign: £
[download]

The fact that you're seeing just the escaped-octal-digit rendition of the byte values suggests that it's not strictly a perl problem.