use File::Find::Rule;

my $directory="../yourdirectory";
  # find all the subdirectories of a given directory
  my @subdirs = File::Find::Rule->directory->in( $directory );
  my $rule =  File::Find::Rule->new;
  $rule->file;
  $rule->name( '*.pl' );
  my @files = $rule->in( $directory );
  
 foreach my $files(@files) {
   
  open   (FILE, "$files");
  while($line= <FILE> ){
  print "$line" if grep  /\buse\b/, $line;
  }
  close FILE; 
 
 }