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    <p>If you want to keep everything in the same file, why not put the logger at the top in a file scoped lexical.</p> <pre><code>GetOptions( do_logging =&gt; \$do_logging ); my $logerr = $do_logging ? sub {logging_code_here()} : sub {}; </code></pre> <p><code>$logerr</code> is now available in any package defined after that point in the same file.</p> <p>However, it is generally faster to structure your logging calls as follows:</p> <pre><code>my $logerr = sub { logging_code_here() }; $logerr-&gt;("some string $some_var") if $do_logging; </code></pre> <p>that way you avoid a subroutine call and the string argument to $logerr does not need to be calculated if logging is off.</p> <p>You can also setup logging levels:</p> <pre><code>$logerr-&gt;("starting loop") if $do_logging; for (@big_array) { $logerr-&gt;("processing $_") if $do_logging &gt; 1; ... } </code></pre> <p>EDIT: While I don't think its the best practice, based on your comments, here is what you are probably looking for (a pragma):</p> <pre><code>use 5.010; use warnings; use strict; BEGIN { # compile time $INC{'log.pm'}++; # block 'require log;' package log; sub is_active {(caller 1)[10]{log}} # test the hints hash sub import { $^H{log} = 1; # set the hints hash for 'log' my $logmsg = (caller).'::logmsg'; # name of caller's sub no strict 'refs'; *$logmsg = sub {print "logging: @_\n" if is_active} # install sub unless *{$logmsg}{CODE}; # unless we did already } sub unimport { $^H{log} = 0; # unset the hints hash } } package MyPkg; use log; logmsg 'hello, world!'; { no log; logmsg 'nope, not here'; } logmsg 'back again'; </code></pre>
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    1. CO@Eric Strom: But then wouldn't I need to reference package main to pull them into my object packages? As in `main::$logerr->("processing $_") if $do_logging > 1;`. The whole point is I'm trying to be concise and reduce the amount of typing and clutter in the code. For different logging / debug levels I simply have different functions, i.e. `loginfo1`, `loginfo2`, etc.. I would think that Perl is smart enough to optimize away a call to an empty function when logging is turned off. Thanks, but I don't think your solution meets my requirements.
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      1. USRobert S. Barnes
    2. CO@Robert S. Barnes => No, that is not the way `my` variables are scoped. Lexicals are not members of a package, but of a scope level, so if a lexical variable is defined at the root scope of a file, it will be visible in every package/block below it in the same file. Additionally, I don't think perl will optimize away the sub call, and calculating the message text before the sub call can be slow (for example if the logging code is in a tight inner loop). by moving the check outside the sub and into the calling code, you could prevent a great deal of unnecessary computation at debug level 0.
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    3. CO@Eric Strom: Thanks for the clarification on visibility. However, when I tried putting the log function at global scope in main it wasn't visible in the packages below it. Are you saying a `my` variable would be visible while one without the my declaration wouldn't? Regarding performance of one vs. the other the only real way to know is testing it.
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