Difference in returning string "x" vs string "x" in a variable

Matt G has asked for the wisdom of the Perl Monks concerning the following question:

Update: Thanks to fglock for answering my question and getting me back to work!

I'm trying to use the larrd graphing tool to output a graph of data in an RRD. The larrd script contains this hash:

my(%graph_c) = (
    SQLDB_Server => {
    hourly => {
        start_sec => "e-48h",
        title => "$host $titleDesc Last 48 Hours",
    },  
    yaxis => $yaxisDesc,
    lines => sub {
        my ($RRD,$service,$graph,$p,$color)=@_;

        $RRD =~ s/:/\\:/g;

        return [
            qq{-u 5},qq{-l 0},
            qq{DEF:stat1=$RRD:$table:AVERAGE},
**          qq{LINE2:stat1#0000FF:$lineName}
        ]
        },
    },
);
[download]

It calls this hash on this line:
@defs = (@defs,@{&{$graph_c{$service}{'lines'}}($RRD,$service,$graph,$p++,&color() )});
With the above setup, the graph comes out fine. I would like to be able to dynamically add multiples of the line marked **. If I try to store the various qq'd strings into a variable, adding as many ** lines as I'd like, then return the variable, the script crashes in apache giving premature header errors.
I am unable to understand exactly what is being returned in the sub, and how to mimic it while returning a variable instead.

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Re: Difference in returning string "x" vs string "x" in a variable by fglock (Vicar) on Nov 04, 2004 at 19:09 UTC
Does this make it crash? `my @r = ( qq{-u 5},qq{-l 0}, qq{DEF:stat1=$RRD:$table:AVERAGE}, qq{LINE2:stat1#0000FF:$lineName}, ); return \@r;` [download] If it works, then try adding this extra line: `push @r, qq{LINE2:stat1#0000FF:$lineName};`	[reply] [d/l] [select]
Re^2: Difference in returning string "x" vs string "x" in a variable by Matt G (Initiate) on Nov 04, 2004 at 19:29 UTC
fglock, your solution worked perfectly. I knew there must be a way to mimick that return statement, just couldn't figure it out. Thank you very much, you've saved me alot of time and effort.	[reply]
Re: Difference in returning string "x" vs string "x" in a variable by bpphillips (Friar) on Nov 04, 2004 at 18:57 UTC
Have you looked at your web servers error logs to get the more specific error message? Have you tried adding: `use CGI::Carp qw(fatalsToBrowser);` [download] to the beginning of your script? Have you tried running your script from the command line to see the error it gives you there? The generic "premature headers" usually indicates a very basic problem with the script (it's dieing because of a syntax error or something similar). Posting the code that doesn't work would help us out in determining what the problem is. --Brian	[reply] [d/l]
Re: Difference in returning string "x" vs string "x" in a variable by Joost (Canon) on Nov 04, 2004 at 18:59 UTC
Adding more of those lines should work) as long as you remember to put a comma at the end of the line. Also, usually error messages for CGI scripts are written to the servers error log. You could have looked there or `use CGI::Carp qw(fatalsToBrowser);` or run the script from the command line. ) where work means: it will compile and run and return that extra line from the sub. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re: Difference in returning string "x" vs string "x" in a variable by elwarren (Priest) on Nov 04, 2004 at 19:10 UTC
How are you creating your array? Are you pushing qq strings on? How are you returning it?	[reply]
Re: Difference in returning string "x" vs string "x" in a variable by Matt G (Initiate) on Nov 04, 2004 at 19:12 UTC
Thanks for the heads up, sorry I didn't have enough information in my original question. I will go and work through the very suggestions. Thank you.	[reply]