Re: Reducing Perl's memory footprint depending on run mode

What you can do is determine at runtime which mode you're in and load the modules based on an if statement in a BEGIN {} block. Such as:

BEGIN: { 
     if( $ENV{fullbore} ) {
          use Big::Module1;
          use Big::Module2;
          use Big::Module3;
     }
     else { 
          use Small::Module1;
     }
}
[download]

Frank Wiles <frank@wiles.org>
http://www.wiles.org

Comment on Re: Reducing Perl's memory footprint depending on run mode Download Code

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Re^2: Reducing Perl's memory footprint depending on run mode by dave_the_m (Monsignor) on Apr 21, 2005 at 15:12 UTC
Er no; all those `use`s need to be `require`s, plus possible calls to `import`. Or `eval 'use ...'` Dave.	[reply] [d/l] [select]
Re^2: Reducing Perl's memory footprint depending on run mode by perrin (Chancellor) on Apr 21, 2005 at 15:13 UTC
I think you'd still have to make those require() instead of use(). Otherwise, they will all get run before evaluating the if statement, even in a BEGIN block.	[reply]
Re^3: Reducing Perl's memory footprint depending on run mode by ides (Deacon) on Apr 25, 2005 at 14:53 UTC
Yup you guys are right, they needed to have been requires not uses. That's what I get for replying without testing my code. :) Frank Wiles <frank@wiles.org> http://www.wiles.org	[reply]
Re^2: Reducing Perl's memory footprint depending on run mode by DrWhy (Chaplain) on Apr 21, 2005 at 15:16 UTC
This is not going to work as written. `use` statements get executed in the compilation phase. `if` statements are executed at runtime. Even inside a `BEGIN` block the code gets compiled first before being executed. The following might work: `BEGIN { if (completely_boring()) { eval <<USE; use Module::A; use Module::B; use Module::Etc; USE } else { eval "use Module::C"; } die $@ if $@; }` [download] Putting the `use` statements inside an `eval` postpones their evaluation till runtime. This only works if the code is in a string rathern than a block. I've also used this trick to set up END blocks conditionally. I vaguely recall that there might be a CPAN module that would let you do this more cleanly, but don't quote me on that. --DrWhy "If God had meant for us to think for ourselves he would have given us brains. Oh, wait..."	[reply] [d/l] [select]