Increase the scope of @dirlist:

use File::Find;

my @dirlist;

sub wanted {
   return unless -d $_;
   push(@dirlist, $File::Find::name);
}

find(\&wanted, shift(@ARGV));

# Use @dirlist here
[download]

Closures come in useful if you'd wish to avoid using a global:

use File::Find;

sub find_dirs {
   my @dirlist;
   find(sub {
      return unless -d $_;
      push(@dirlist, $File::Find::name);
   }, @_);
   return @dirlist;
}

{
   # Not a global.
   my @dirlist = find_dirs(shift(@ARGV));

   # Use @dirlist here
}
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Yet another way. This one uses dynamically scoped variables:

use File::Find;

sub wanted {
   return unless -d $_;
   push(@File::Find::matches, $File::Find::name);
}

sub find_it {
   local *File::Find::matches;
   find(@_);
   return @File::Find::matches;
}

{
   # Not a global.
   my @dirlist = find_it(\&wanted, shift(@ARGV));

   # Use @dirlist here
}
[download]

Update: Added 2nd snippet.
Update: Added 3rd snippet.