#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my $dir_to_process = '.';
my %stuff_to_store; 

# Get all of the txt files and put them into the @files array
opendir(DH, $dir_to_process) or die "Cannot open $dir_to_process: $!";
my @files = grep { /\.txt$/i } readdir(DH);
closedir(DH);

my $fullname = "$dir_to_process/$file";

# Process each file
for my $file (@files) {
  open(my $fh, "<", $fullname) or die(qq(Unable to open '$fullname' for reading: $!);

  # I like to explicitly set a $line variable, rather than implicitly using $_
  while (my $line = <$fh>) { #cycling through to find happy
    if ($line =~ /happy/) { 

      # Here, I'm using %stuff_to_store as a hash of array references
      # The hash key is the concatenation of the path and the file name
      # The value for each key is an array reference that contains lines  
      # like:
      #   "Line 123: <this is the text of the found line>"

      push(@{$stuff_to_store{$fullname}, "Line $.: $line");
    }
  }
  close ($fh);
}
print Dumper(\%stuff_to_store);