Include module at compile time with condition

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

I have a snippet like this

 
BEGIN {
    require "call_simulator.pm" ;

    use constant {
        START           => 1000 ,
        NO_OF_CALLS     => 1 ,
        DEBUG           => 1 ,
        DET_DEBUG       => 1 ,
        TOTAL_TIME      => 1 ,
        DETAILED_TIME   => 1 ,
        RESPONSE        => 1 ,
        SLEEP           => undef ,
        MICRO_SEC       => 1 ,
    };

    # This works well 
    if ( MICRO_SEC ) {
        eval "use Time::HiRes qw (time )" ;

    }
    # This works
    # use if ( MICRO_SEC ) , "Time::HiRes" ;

    # This won't work  
    # use if ( MICRO_SEC ) , "Time::HiRes qw(time)" ;
    # ERROR : 
   # Can't locate Time/HiRes qw(time).pm in @INC (@INC contains: /etc/
+perl /usr/local/lib/perl/5.10.0 /usr/local/share/perl/5.10.0 /usr/lib
+/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/
+local/lib/site_perl .) at /usr/share/perl/5.10/if.pm line 13.


}
[download]

I just wanted to include the Time::HiRes module with a time
function at a compile time with a condition
Using eval statement its possible !
but my question is how can I achieve this with the "use if" to include a module with a function !

Comment on Include module at compile time with condition Download Code

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Re: Include module at compile time with condition by Corion (Patriarch) on May 07, 2011 at 07:12 UTC
See the documentation for the "if" module. I'm not sure how to explain things better than the documentation of that module. Alternatively, use the mechanism outlined in use, but that is basically what if does.	[reply]
Re: Include module at compile time with condition by Eliya (Vicar) on May 07, 2011 at 07:11 UTC
`use if ( MICRO_SEC ) , "Time::HiRes", qw(time) ;` [download]	[reply] [d/l]
Re^2: Include module at compile time with condition by abubacker (Pilgrim) on May 07, 2011 at 07:20 UTC
Thats what im looking for Thanks a lot I made a slight change ( of course both are same ) for the coding style `use if ( MICRO_SEC ) , Time::HiRes => qw(time) ;` [download]	[reply] [d/l]
Re^3: Include module at compile time with condition by Eliya (Vicar) on May 07, 2011 at 07:37 UTC
Note that the fat comma doesn't work here under `use strict` (i.e., you'd still need to quote the module name): `#!/usr/bin/perl use strict; use if ( 1 ) , Time::HiRes => qw(time) ;` [download] `$ ./903506.pl Bareword "Time::HiRes" not allowed while "strict subs" in use at ./903 +506.pl line 3. Execution of ./903506.pl aborted due to compilation errors.` [download]	[reply] [d/l] [select]
Re^4: Include module at compile time with condition by tchrist (Pilgrim) on May 08, 2011 at 00:30 UTC
Re: Include module at compile time with condition by John M. Dlugosz (Monsignor) on May 07, 2011 at 07:11 UTC
Your answer is given by the first example in the Synopses for the if module.	[reply]
Re: Include module at compile time with condition by Khen1950fx (Canon) on May 07, 2011 at 07:59 UTC
I tried it like this---the fat comma worked in this case because I added a left curlie and a right curlie to `use constant`. Without the curlies, MICRO_SEC becomes a bareword: `#!/usr/bin/perl use strict; use warnings; use constant ({ START => 1000, NO_OF_CALLS => 1, DEBUG => 1, DET_DEBUG => 1, TOTAL_TIME => 1, DETAILED_TIME => 1, RESPONSE => 1, SLEEP => undef, MICRO_SEC => 1, }); BEGIN { eval { require "call_simulator.pm"; use if MICRO_SEC, 'Time::HiRes' => qw(time); } }` [download]	[reply] [d/l] [select]
Re: Include module at compile time with condition by Nikhil Jain (Monk) on May 07, 2011 at 09:09 UTC
Some general remark: "use Readonly" - Facility for creating read-only scalars, arrays, hashes. instead of "use constant" It would be nice to see this section COMPARISON WITH "use constant" in Readonly	[reply]
Re^2: Include module at compile time with condition by Anonymous Monk on May 07, 2011 at 09:15 UTC
Some general remark: See Where should I post X?, new questions go in Seekers of Perl Wisdom, thoughts in Meditations Thanks	[reply]
Re: Include module at compile time with condition by wind (Priest) on May 07, 2011 at 17:20 UTC
Yet another slightly different way to accomplish this. Note the BEGIN is redundant `use constant ({ START => 1000, NO_OF_CALLS => 1, DEBUG => 1, DET_DEBUG => 1, TOTAL_TIME => 1, DETAILED_TIME => 1, RESPONSE => 1, SLEEP => undef, MICRO_SEC => 1, }); use if MICRO_SEC, qw(Time::HiRes time);` [download] And before learning about the if package, I'd do the following: `BEGIN { if (MICRO_SEC) { require Time::HiRes; Time::HiRes->import('time'); } }` [download]	[reply] [d/l] [select]