Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!jpl-devvax!lwall
From: lwall@jpl-devvax.jpl.nasa.gov (Larry Wall)
Newsgroups: comp.lang.perl
Subject: Re: eval failures - in a commented line
Keywords: cgrep, eval bug report
Message-ID: <1991Jun24.212752.11784@jpl-devvax.jpl.nasa.gov>
Date: 24 Jun 91 21:27:52 GMT
References: <1991Jun21.194148.24804@cbnewsh.att.com>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Distribution: na
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 26

In article <1991Jun21.194148.24804@cbnewsh.att.com> ijk@cbnewsh.att.com (ihor.j.kinal) writes:
: While trying to extend cgrep', I ran into an interesting problem.
: The eval part of the program failed [silently].  Since I had made a number
: of changes, I tried commenting them out, to no avail.  Finally, by deleting
: lines, I determined the failure was within a commented line that
: had a print format:
: #	print \$ary[\$ind], "\n";
: 	
: By deleting the "\n", then program then seemed to work as before.
: 
: Is this a bug, or what???

It's what.

You're obviously evaluating this in a double-quote context, or you
wouldn't be backwhacking the dollar signs.  (It's also obvious that
you're not using double quotes to get the double-quote context, or you
WOULD be backwhacking the double quotes.)  Recall that double-quote
context also interpolates things like \n.  Recall also that comments
run to the next newline, and you'll see that the second double quote
above is on the next line after the comment, if the newline gets
interpolated too early, which it is.  It doesn't matter without the
comment, since Perl can have newlines embedded in a quote.  To fix it,
put \\n instead.

Larry