#!/usr/bin/perl -w
use strict;

foreach (<DATA>) {
   print "$1\n" if (m|(\w+\.bld)(?!\S*#)|)
}

__DATA__
../nbssbase/ip/bld/l?ibipGH040.bld:57:#   Reflecting change of eni.cxx
../nbssbase/ip/bld/l?ibipGH060.bld:60:#   Reflecting change of eni.cxx
../nbssbase/ip/bld/l?ib.bld:17:eni.cxx