Unique words in lyrics

lyrics.pl

#!/usr/bin/perl
use strict;
use warnings;

my $lyric_file = $ARGV[0];
my @unique_words = [];
my $total_words = 0;

open(my $lyrics, '<:encoding(UTF-8)', $lyric_file)
    or die "Could not open file '$lyric_file' $!";

open(my $unique_file, '>:encoding(UTF-8)', 'unique_file.txt')
    or die "Cannot open file 'unique_file.txt' $!\n";

while (my $row = <$lyrics>) {
    my @mod_row = split(/ /, $row); 

    foreach my $i (0 .. $#mod_row) {
        $total_words++;
        unless (grep(/^$mod_row[$i]$/, @unique_words)) {
            my $word = $mod_row[$i];
            $word =~ s/,//g;
            push @unique_words, $word;
        }
    }
}

print $unique_file join(" ", @unique_words);
print $unique_file "There are " . scalar @unique_words . "/$total_words unique words in the song provided.\n";

close($unique_file);
close($lyrics);