You've gotten lots of perl solutions, so let me offer a non-perl one. If you have GNU hostname on your machine1, use the -i option to get the machines IP address. 
$ hostname -i
63.150.14.148

[download]
1 any flavor of linux or other machine with the standard set of GNU tools installed.

-Blake

In reply to Re: Getting net addy on localhost? by blakem
in thread Getting net addy on localhost? by r.joseph

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