use strict;
use warnings;
my $dir = shift;
my $criteria = shift;
$criteria = "" unless defined $criteria;
die "Usage: $0 directory" unless defined $dir;
opendir DIR, "$dir" or die "Could not open $dir: $!\n";
my @files=grep(/$criteria/, readdir DIR);
print $#files+1, " files\n";
chdir $dir;
foreach my $file (@files) {
  # actions go here
}
closedir DIR;