Re: How do I dynamically declare a package name for

I use this for long-running mod_perl modules:

my $class = fetch_from_somewhere;
my $object;
eval {
    $object = $class->new;
};
if ($@) {
    eval ("use $class");
    die ($@) if $@;
    $object = $class->new;
}
[download]

This will include $class.pm only once, the first time it is refferenced. Ideal for mod_perl modules. So performance penalty of compiling "use $class .." code is suffered only once.

Comment on Re: How do I dynamically declare a package name for Download Code

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Re: Re: How do I dynamically declare a package name for by hdp (Beadle) on Apr 27, 2001 at 16:09 UTC
This is actually unnecessary. Both use and require will look in `%INC` to make sure the file has not yet been included before loading it. (use will still call import again unless you explicitly pass it an empty list of symbols to import.) hdp.	[reply] [d/l]
Re: Re: Re: How do I dynamically declare a package name for by gildir (Pilgrim) on Apr 27, 2001 at 21:14 UTC
Yes, but there is big difference when calling: `eval { $object = $class->new; };` [download] and `eval " $object = $class->new; ";` In the former case, code is compiled as soon as it is first encountered by perl compiler, that is at compile time and it is compiled only once. While in the later case the code is compiled at run-time and is compiled every time the eval() is run. There is no way to do `eval { use $class; };` so I must use `eval " use $class; ";` version, and I try to execute it as seldom as possible.	[reply] [d/l] [select]