open( LIST, "mystopwords.txt" ) or die "$!";
my @stopwords = <LIST>;  # assuming one stop word per line
close LIST;
chomp @stopwords;

my $stopregex = join '|', @stopwords;

# ... now, when you go to delete stopwords from $_,
# it goes like this:

   s/\b(?:$stopregex)\b//g;


##</code><code>##

my %stopwd;
open( LIST, "my_stopwords.txt" ) or die "$!";
while (<LIST>) {
    chomp;
    $stopwd{$_} = undef;  # assume one word per line
}
close LIST;

# now, to remove stopwords, split the input data ($_) on \b
# and check each token:

my $filtered = join '', map { exists($stopwd{$_}) ? '':$_ } split /\b/;