From the prompt: grep -l keyword *

Lazy perl way: $filename = `grep -l keyword *`

or

# Exits as soon as a match is found.
# only reads a line in at a time, not the entire file.

sub find_file {
   my ($dir_name, $keyword) = @_;

   my $file_name;
   my $file_path;

   my $dh = DirHandle->new($dir_name)
   or die("Can't read directory: $!.\n");

   while (defined($file_name = $dh->read())) {
      $file_path = "$dir_name/$file_name";

      next if ($file_name eq '.');
      next if ($file_name eq '..');
      next unless (-f $file_path);

      my $fh = FileHandle->new($file_path, 'r')
      or warn("Can't read file $file_name: $!.\n");

      while (defined($_ = $fh->getline())) {
         return $file_name if (index($_, $keyword) != -1);
      }
   }

   return undef;
}
[download]