#!/bin/perl


 my @csv2 = (); # Creates new empty array @csv2

      open CSV2, "<csv2" or die; # Creates the file handle CSV2, input
+s the data from csv2 into CVS2

      @csv2=<CSV2>; # populates @csv2 array with data from file handle
+ CSV2
      close CSV2;

      my %csv2hash = ();  # Creates empty hash csv2hash

      for (@csv2) {            # for data in @csv2 array
      #chomp;

       my ($title) = $_ =~ /^.+?,\s*([^,]+?),/; #/define the data whic
+h is the title
#Indicate that title data will input into csv2hash
        $csv2hash{$_} = $title;

}

foreach my $csv2 (keys %csv2hash) { # iterates over all the keys in %c
+sv2hash, assigning each one to $csv2



    my $value = $csv2hash{$csv2};



print "$csv2\n"; # This prints the data line by line in the csv2
[download]

The keys of %csv2hash are the lines:

for (@csv2) {            # for data in @csv2 array
      my ($title) = $_ =~ /^.+?,\s*([^,]+?),/;
      $csv2hash{$_} = $title;
}
[download]

Here, $_ (the current line) is used as a key into %csv2hash.

What does this bit of the script do?  my @matches   = ( $value=~/\b$word\b/ig ); specifically the  \b  \b/ig bits?