Testing if machine has LWP... not working

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

I have a small script which runs on a number of different servers. Some of these servers do not have LWP module installed (and I cannot install it on them). I have the following eval test to determine if LWP is available...

if (eval "require LWP::UserAgent; 1") {

    my %post = ('key' => 'value');
    my $ua = LWP::UserAgent->new();

    my $content = $ua->post("http://www.mydomain/post.cgi",[%post])->a
+s_string;

    #do something with the content ...
} else {
    print "LWP not available";
}
[download]

This works quite nicely on most servers... Most servers have LWP and the POST works fine. Some don't and they get the else message above. However, a few servers report the following error:

Can't locate object method "post" via package "LWP::UserAgent" (perhap
+s you forgot to load "LWP::UserAgent"?) at (eval 2) line 1.
[download]

How can I avoid this? Is the eval not a suitable way to test of LWP is available? Is there a better way to do this? Thanks so much...

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Re: Testing if machine has LWP... not working by ikegami (Patriarch) on Nov 22, 2006 at 02:06 UTC
IIRC, `post` didn't exist in older versions of LWP::UserAgent. It's definitely consistent with the results you are getting. Instead, create a request using HTTP::Request::Common and pass it to `$ua->request`.	[reply] [d/l] [select]
Re: Testing if machine has LWP... not working by GrandFather (Saint) on Nov 22, 2006 at 01:43 UTC
The documentation for post in LWP::UserAgent mentions using HTTP::Request::Common to do the work. Is it possible that that module is not available on some of your servers? DWIM is Perl's answer to Gödel	[reply]
Re: Testing if machine has LWP... not working by Cabrion (Friar) on Nov 22, 2006 at 01:44 UTC
You should be checking $@ for an error after an eval.	[reply]
Re^2: Testing if machine has LWP... not working by ikegami (Patriarch) on Nov 22, 2006 at 02:02 UTC
No need. `eval` returns undef on expection. Otherwise, it returns true because of the `1;`. It would return true even without the `1;` because `require` always returns true or an exception. Incidentally, `eval EXPR` is not needed here. `eval BLOCK` suffices. `if (eval { require LWP::UserAgent })` [download]	[reply] [d/l] [select]
Re: Testing if machine has LWP... not working by Anonymous Monk on Nov 22, 2006 at 15:31 UTC
Don't use string-eval, use block eval instead: `eval { require LWP::UserAgent}`	[reply] [d/l]