LWP and barewords under strict

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

Hello PerlMonks!

I have some broken code here, that is perplexing me. I am using LWP::UserAgent to pull information off of a website.

I have had no problem with this until I wrote the following bit of (broken) code:

#!/usr/bin/perl -w

use strict;
use HTTP::Request::Common qw(POST);
use LWP::UserAgent;

my ($ua, $req, $chrom, $start, $end, $db, $check);

$chrom="7";
$start="117287204";
$end="117475903";
$db="hg11";

open (GENOMIC, ">genomic_dna") || die "Error: Can't open genomic_dna: 
+$!";

$ua = LWP::UserAgent->new;
$req = POST 'http://genome.ucsc.edu/cgi-bin/hgText',
    [
     hgsid => '6765675',
     g => 'htcGetDna2',
     c => 'chr'.$chrom,
     l => $start,
     r => $end,
     db => $db,
     hgc.dna.out1 => 'lc',
     boolshad.hgc.dna.rc => '1',
     Submit => 'Submit'
     ];

print GENOMIC $ua->request($req)->content;
close (GENOMIC) || die "Error: Can't close genomic_dna: $!";
[download]

The problem is that if I paste the relevant command into a browser - everything is fine, but I've broken it down for an LWP request.

Attempting to run this leads to the following:

[dswan@ashtaroth useful]$ ./genomic.pl
Bareword "hgc" not allowed while "strict subs" in use at ./genomic.pl 
+line 18.
Bareword "dna" not allowed while "strict subs" in use at ./genomic.pl 
+line 18.
Bareword "boolshad" not allowed while "strict subs" in use at ./genomi
+c.pl line 18.
Bareword "hgc" not allowed while "strict subs" in use at ./genomic.pl 
+line 18.
Bareword "dna" not allowed while "strict subs" in use at ./genomic.pl 
+line 18.
Execution of ./genomic.pl aborted due to compilation errors.
[download]

Even to me this obviously means LWP doesn't much like the '.' in the LWP request. I've tried to escape them, quote them (double and single), but to be honest I don't see why it should be a big issue (except the program returns the wrong data obviously :P)

Any ideas?

As always the help is greatly appreciated

Bukowski - aka Dan (dcs@black.hole-in-the.net)
"Coffee for the mind, Pizza for the body, Sushi for the soul" -Userfriendly

Comment on LWP and barewords under strict Select or Download Code

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Re: LWP and barewords under strict by suaveant (Parson) on Jul 09, 2002 at 13:59 UTC
And it shouldn't... . is string concatenation in perl, so perl is trying to concatenate barewords... with => perl allows you to not quote the string on the left, but only very simple strings without . or spaces and the like... put your left hand side strings in quotes and all will be well... - Ant - Some of my best work - (1 2 3)	[reply]
Re: Re: LWP and barewords under strict by Bukowski (Deacon) on Jul 09, 2002 at 16:35 UTC
Yes this worked a treat (and I had tried it before!). Of course it worked properly after I realised there was a horrendus typo in the LWP request....... D'OH! Bukowski - aka Dan (dcs@black.hole-in-the.net) "Coffee for the mind, Pizza for the body, Sushi for the soul" -Userfriendly	[reply]
Re: LWP and barewords under strict by Abigail-II (Bishop) on Jul 09, 2002 at 14:03 UTC
You are getting syntax errors. That has nothing to do with LWP, but all the do with your code. You have `hgc.dna.out1`, three bare words that you are trying to concatenate. With `use strict`, that's a syntax error. You have to use quotes. Abigail	[reply] [d/l] [select]
Re: LWP and barewords under strict by hacker (Priest) on Jul 10, 2002 at 11:10 UTC
A few comments: You never use $check. One thing I've taken on as a habit is to declare the variables I use as 'my' when I use them. When you pre-declare them in one string as you have with `my ($ua, $req, $chrom, $start, $end, $db, $check);`, you increase the chance of error when you remove/add them later, as you have in this script. One possible solution is as follows: `my $ua = LWP::UserAgent->new; my $chrom = "7"; my $start = "117287204"; my $end = "117475903"; my $db = "hg11"; my $url = "http://genome.ucsc.edu/cgi-bin/hgText";` [download] (I also like to indent for readability, but that's more a matter of personal style.) You also are not properly separating your POST object. It should look something like: `# Indented again my $request = POST $url, ['hgsid' => "6765675", 'g' => "htcGetDna2", 'c' => 'chr'.$chrom, 'l' => $start, 'r' => $end, 'db' => $db, 'hgc.dna.out1' => 'lc', 'boolshad.hgc.dna.rc' => '1', 'Submit' => 'Submit' ];` [download] Note the use of the single quotes around the key, which was missing in your original script. Adding the above fixes allows your code to work as intended.	[reply] [d/l] [select]


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