The * quantifier means "zero or more times". It seems your data contain commas at line ends, so the non-comma is matched zero times. $1 is then the empty string: 
#!/usr/bin/perl
use warnings;
use strict;

my %denovo;

while (my $line = <DATA>){
    chomp $line;
    if ($line =~ /([^,]*)$/){
        my $name = "$1";
        print "name is $name\n";
        $denovo{$name} = $line;  # Quotes not needed.
    }
}

print "hash denovo is:\n";
while( my( $key, $value ) = each %denovo ){
    print "$key: $value\n";
}

__DATA__
no comma
comma, in the middle
comma at the end,

previous line was empty

[download]
($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

[download]

In reply to Re: Why are my hash keys undefined? by choroba
in thread Why are my hash keys undefined? by biologistatsea

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