I'd suggest a similar trick to what we do in C/C++ when the wrapped library is too large to individually load each function. Cheat. 

package Wrap::PDL;

use PDL;
use base 'Exporter'; # for simplicity...

sub my_method {
  # Code
}

1;

[download]
And then, in your module, just do something like this: 
my $has_PDL = eval "use Wrap::PDL qw(my_method); 1";

#...

if ($has_PDL)
{
  my_method(0, 0, $value);
}

[download]
Well, either that, or just require PDL to be installed :-P

Update: Fletch pointed out that I had $has_PDL in double-quotes and needed either backwhacking or to be in single-quotes. So I removed it altogether. This method takes advantage of tye's trick on ensuring whether an eval executes properly or not by checking its return code rather than $@, and ensuring that correct execution actually does result in a true value. I can also be more confident in using lexical variables here. I'm pretty sure eval STR can use lexicals declared outside of its scope, but here I don't even have to think about that.

Another alternative would be: 

my $has_PDL = eval {
  require Wrap::PDL;
  Wrap::PDL->import(qw(my_method));
  1;
}

[download]
which is probably better in that I prefer using eval BLOCK over eval STRING whenever possible.

In reply to Re: Conditional loading of methods by Tanktalus
in thread Conditional loading of methods by bruno

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.