I've tried to improve your code, and I have tested what I am posting here.

You have a couple of problems. The first one is that you are creating a number of unnecessary arrays with your extra foreach loops. I've tried to optimize that by using keys with hashes as opposed to creating temporary lookup arrays, and then creating a subroutine to handle reading in the files, etc. When you're done with a file, it is a good idea to close it to avoid leaving dangling filehandles.

The other thing has already been pointed out. If you look at the Lingua::EN::MatchNames documentation, you can see it expects fn1, ln1, fn1, ln2. I fixed that, kind of (see my comment). The name_eq() function will return undef if there is no possible match, so I adding handling for that as well. That accounts for the "uninitialized value" warnings.

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

use Lingua::EN::MatchNames;


my $termfile = shift;
my $userfile = shift || die "Usage: $0 TERMFILE USERFILE\n";

my %curlookup = getlist($userfile);
my %termlookup = getlist($termfile);


open my $dfh, ">", "dup.$userfile");

foreach my $termusername (keys %termlookup) {
        NameComp( $termlookup{$termusername} )
}

close $dfh;

#  getlist takes a filename as an argument
sub getlist {
    
    my $filename = shift;
    
    my $counter;
    my %results;
    
    open my $fh, "<", "$filename";
    
    while ( <$fh> ) {
        chomp;
        ++$counter;
        next unless m/[A-Za-z]/;
        $results{$counter} = $_;
        print "Adding user $counter $_ from file \'$filename\' to hash
+\n";
    }

    close $fh;
        
    return %results;
}

sub NameComp { # no parens, this is not a function prototype
        
    my $compname = shift;
    
        foreach my $curusername (keys %curlookup) {
        print "Comparing \'$compname\' to \'$curlookup{$curusername}\'
+\n";
        
        # This method is not good because it assumes a ' FN -SPACE- LN
+ ' format
        my @compname = split /\s+/, $compname;
        my @curname = split /\s+/, $curlookup{$curusername};
        
                my $name_score = name_eq( $compname[0], $compname[1], 
+$curname[0], $curname[1] );
        if ( $name_score ) {
            if ( $name_score >= 80 ) {
                print "Found Match $curlookup{$curusername} with a sco
+re of $name_score.\n\n";
            }
        }
        else {
            print "\t\tNo possible match.\n\n";
        }
        }
}
[download]

Best of luck to you.