Sometimes using a split can work out better than a full blown regex. Consider this:

#!/usr/bin/perl
use strict;
use warnings;

my $row = 'We_need_feed';

my ($first, $middle, $last) = split /_/, $row;

print "first=$first, middle=$middle, last=$last\n";

#Update: just demo of indices:
($first, $middle, $last) = (split (/_/,$row))[0,1,-1];

print "middle=$middle\n";

__END__
Prints:
first=We, middle=need, last=feed
middle=need
[download]