Re: using 'use' conditionally (require instead of use)

[ybiC]

in reply to using 'use' conditionally

If I'm not mistaken, you want to require instead of use in your eval block.   Here's how I did similarly a while back:

my $have_SWE;
BEGIN {
  $have_SWE = 0;
  eval { require Spreadsheet::WriteExcel };
  unless ($@) {
     Spreadsheet::WriteExcel->import();
     $have_SWE = 1;
  }
}
if ($have_SWE == 1) { ... }

If memory serves, I picked that up from something merlyn once said or posted.
    cheers,
    Don
    striving toward Perl Adept
    (it's pronounced "why-bick")

Update:
Super Search for "module installed" is what lead me to this thread, where I learnt of BEGIN, eval, and require.

Update:
After discussing with brother BUU, the lone advantage I can see of BEGIN... eval is that it allows you to include a more user-friendly message in the event that Tk isn't installed.   As always, Wiser Monks Than I may very well rightly say that I'm fullabeans.   {grin}

Untested, but perhaps a wee bit cleaner than my original code example:

my $have_Tk;
BEGIN {
  $have_Tk = 0;
  eval { require Tk };
  $have_Tk = 1 unless ($@);
}
if ($have_Tk == 1) { ... }

[BUU]

Why bother evaling? Just do if($opt_g){require Tk;}

[chromatic]

What if the require fails?

[tye]

Then you can't run with the -g mode and the user gets a good explanation as to why. I agree with BUU, drop the eval entirely.

        - tye

[xafwodahs]

When I switch the 'use' to a 'require', I can indeed determine if the module is not installed and catch that.

However, if the module *is* installed, the Tk code fails to function. There are no errors or anything - the script just exits. I actually placed a 'print' after the MainLoop call, and I see the print output.

It seems to make no difference whether I call Tk->import;
It seems to make no difference if I place Tk:: before the tk subroutines.

bizarre...