How do I check whether a Perl module is installed? [duplicate]

Question

I'm writing a small Perl script that depends on some modules that might be available, so during the installation I would have to check if everythings there. I could just write use some::module and see if an error comes up, but a short message like "You need to install some::module" would be more helpful for endusers.

I also could just search every directory in @INC, but as it's Perl, there has to be an easier way.

Answer 1

How about:

die "Some::Module missing!" unless(eval{require Some::Module});

Answer 2

perl -MSome::Module -e ';'

Whoops, misread the question. I thought you wanted to know in a one-off instance, not discovering it in a recoverable manner. I always use something like this:

sub try_load {
  my $mod = shift;

  eval("use $mod");

  if ($@) {
    #print "\$@ = $@\n";
    return(0);
  } else {
    return(1);
  }
}

Which you use like this:

$module = 'Some::Module';
if (try_load($module)) {
  print "loaded\n";
} else {
  print "not loaded\n";
}

Answer 3

I have a little script that lists all the Perl modules on my system;

#!/usr/bin/perl

use ExtUtils::Installed;
my $instmod = ExtUtils::Installed->new();
foreach my $module ($instmod->modules()) {
    my $version = $instmod->version($module) || "???";
    print "$module -- $version\n";
}

Inside that foreach loop you might want to do some thing like;

my $match;
if ($module =~ /$match/) {
  print "Found $match: $module\n";
}