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

my %new_list;

read_n_work_file( 'masterlist.txt', sub { undef $new_list{ $_[0] } } );

read_n_work_file( 'removelist.txt',
    sub { delete $new_list{ $_[0] } if exists $new_list{ $_[0] } } );

print join "\n" => keys %new_list; # print to a new file

sub read_n_work_file {
    my ( $file, $workout ) = @_;

    open my $fh, '<', $file or die "can't open file:$!";
    while (<$fh>) {
        chomp;
        $workout->($_);
    }
}