"use" file...

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

I am trying to do this, but I keep getting an error:

use $req_File;
$req_File is the result of a check.

the value of $req_File is in this format: Crypt::IDEA, Of course it is one of my personal Modules I created, but that is another story. If I just put use MyModule::Name;
then it works fine, but If I put what I have I get this error here:

syntax error at Notify.cgi line 16, near "use $req_file" Notify.cgi had compilation errors.

Am I allowed to put a "use" with a Perl String?

If so, what am I doing wrong?
If not, I guess that is my problem ;o)

thx,
Richard

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•Re: "use" file... by merlyn (Sage) on Feb 08, 2003 at 17:29 UTC
First, `use` is a compile-time operation, so hopefully, you have some way of getting the value early enough in the process. If not, you'll have to switch to `require`. Which brings me to the second point. You can't provide a variable string to `use`, but you can decompose it to its definition: a `BEGIN` block around a `require` and a method call: `## replace "use $string @imports" with: BEGIN { (my $filename = $string) =~ s,::,/,g; # unix/windows only require $filename; $string->import(@imports); }` [download] -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l]
Re:(merlyn) Re: "use" file... by demerphq (Chancellor) on Feb 08, 2003 at 23:25 UTC
The other approach is to `BEGIN { eval "use $string \@imports; 1" or die "Failed lazy use(): $@"; }` [download] Er. pfaut already said this. Sorry. :-) Update: As merlyn said below. You need to be real careful that $string is completely under your control. You dont want to be reading it froma file for instance. At least not without some serious data cleaning first. --- demerphq my friends call me, usually because I'm late....	[reply] [d/l]
•Re: Re:(merlyn) Re: "use" file... by merlyn (Sage) on Feb 09, 2003 at 17:45 UTC
I don't like to encourage such a casual use of `eval` unless it it also stated in big red letters that control over the contents of `$string` there absolutely essential. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re: "use" file... by pfaut (Priest) on Feb 08, 2003 at 17:31 UTC
'use' is parsed at compile time. Unless the 'use' statement and the assignment to $req_File are inside a BEGIN block, I would expect it to fail since no value has been assigned to $req_File. I'm not sure 'use' accepts a scalar as an argument. If you need the functionality of 'use' at runtime, use `eval "use $req_File"`. `--- print map { my ($m)=1<<hex($_)&11?' ':''; $m.=substr('AHJPacehklnorstu',hex($_),1) } split //,'2fde0abe76c36c914586c';` [download]	[reply] [d/l] [select]