I tried this:

#!/usr/bin/perl

use strict;
use warnings;
use File::Util;
use File::Spec;

my @dirs = shift @ARGV;

my($f) = File::Util->new();
(@dirs) = $f->list_dir(
              @dirs, 
              '--dirs-only',
              '--no-fsdots',
              '--with-paths');

foreach my $dir(@dirs) {
        foreach ($dir) {
            my (@ext) = ('*.so', '*.o', '*.a');
            my $path = File::Spec->catfile($dir, "*.@ext") . "\n";
            if (not glob($path)) {
                print "No @ext in $dir\n";
            }
            else {
                  print "OK\n";
            }
      }
}
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Update: replaced if ($dir) with foreach ($dir)