undefined function _() ?

[Hanser, Kevin]

hmmm... this is most likely my fault, but what exactly does  it mean when
horde says "call to undefined function _()".  I'm trying to get IMP 2.3
working so I can play around and check it out.  I followed the instructions
included with it (mostly :)  Maybe this is one of those things I thought I
didn't need to install....?
It's occuring because of echo statements that look like echo _("something").
What is the purpose of the _ in front of the parentheses?  I'm fairly
familiar w/php, but haven't seen this used before...

thanx

Kevin Hanser
System Administrator
Merchant Internet Group
kevin@MerchantInternetGroup.com