I've added the Data::Dumper lines as you requested:

#!/usr/bin/perl                           

use warnings;
use strict;
use Lingua::JA::Numbers;

my $converted = "converted_numbers.csv";
my $len = $ARGV[0];
my (@numList, @rom, @kana, @kanji, %randList);
open(OUTFILE, ">$converted");
binmode OUTFILE, ":utf8";

for (my $i=0; $i<$ARGV[1]; $i++) {
    my $genlen = int rand($len);
    my $max = 1 . 0 x $genlen;
    my $num = int rand($max);
    $randList{$num} = 1;
}

use Data::Dumper;
print "Data Dump:\n";
print Dumper(\%randList) . "\n";

print "randList length: " . (scalar keys %randList) . "\n";

@numList = keys %randList;

print "Length numList: " . (scalar @numList) . "\n";

for my $num (@numList){
        my $jaRom = Lingua::JA::Numbers->new($num, {style=>'romaji'});
        my $jaKana = Lingua::JA::Numbers->new($num, {style=>'hiragana'
+});
        my $jaKanji = Lingua::JA::Numbers->new($num, {style=>'kanji'})
+;
        push(@rom, $jaRom);
        push(@kana, $jaKana);
        push(@kanji, $jaKanji);
}

my (@hyphens, @noHyphens);
for my $strg (@rom){
        @hyphens = Lingua::JA::Numbers::to_string($strg);
        for my $val (@hyphens){
                $val =~ s/-//g;
        }
        push(@noHyphens, join(" ", @hyphens));
}

@rom = @noHyphens;

my $size = scalar @numList;
print $size . "\n";
foreach (my $i=0; $i<$size; $i++){
        print OUTFILE $numList[$i] . "," . $rom[$i] . "," . $kana[$i] 
+. "," . $kanji[$i] . "\n";
}

close OUTFILE;
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I've also added a newline at the end of the second print statement which has exposed something else:

msnyder@msnyder:~/bin> ./num-to-jp4.pl 6 20
Data Dump:
$VAR1 = {
          '48766' => 1,
          '9732' => 1,
          '33' => 1,
          '66526' => 1,
          '328' => 1,
          '4344' => 1,
          '438' => 1,
          '0' => 1,
          '55' => 1,
          '6' => 1,
          '5148' => 1,
          '182' => 1,
          '3' => 1,
          '46726' => 1,
          '3319' => 1,
          '59' => 1,
          '2851' => 1,
          '652' => 1
        };

randList length: 18
Length numList: 18
18
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