'remaining 90' is relevant to 100 unique names in FILE2.
assuming, that's not exactly what you meant (remaining can be lower than 90 if there are repetitions in FILE2), this code should work for you:

use strict;
use Tie::File;

# read first file
open my $fh, '<', 'FILE1'
    or die "can't open FILE1\n";
chomp(my @file1 = <$fh>);
close $fh;

# remove from second file
tie my @file2, 'Tie::File', 'FILE2' 
    or die "can't open FILE2\n";

foreach my $x (@file1) {
    @file2 = grep {!/^$x$/} @file2;
}

untie @file2;
[download]

HTH,
Mickey