in reply to grep unmatch error

If @tokens and @stopwords are matched on the complete word, you can perform the comparison much faster by converting @stopwords into a HASH. 
perl -E 'my @tokens=qw|this that other foo bar baz|;
         my %stopwords=qw|that 1  foo 1|;
         say for grep {!$stopwords{$_}} @tokens'
__OUTPUT__
this
other
bar
baz

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In Section Seekers of Perl Wisdom