You pushed my "$1 used outside the context of a conditional" button here. That'd be failed in a code review if I were running the show. And yes, after I stared at the code for a minute or so, I can see that the assertion from the previous line ensures that there's always a match. But in that case, why not make the match, the match!

while (<DATA>) { 
  chomp; 
  s/#.*$//; 
  next unless /([^\s]+)/; 
  push(@enabled_lines, $1); 
}
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There: it's now clear to me that we can't get to the push unless the match succeeds. I'd let this stand in a code review, but if I was looking for further optimization, I'd just keep pressing forward for more clarity:

while (<DATA>) { 
  chomp; 
  s/#.*$//; 
  push(@enabled_lines, $1) if /([^\s]+)/;
}
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Nicer. Tighter. Dare I say, "faster" as well? But I see some equivalances that are down in the "nice" category (first was "must", second was "want", now "nice"):

while (<DATA>) { 
  chomp; 
  s/#.*$//; 
  push @enabled_lines, $1
    if /(\S+)/;
}
[download]

There. Clean, maintainable, pretty. I don't know if this does what the original poster wanted, but I didn't change the meaning at all from the node to which I'm replying.

-- Randal L. Schwartz, Perl hacker