You can create a regular expression once and reuse it on each string.

#!/usr/bin/env perl

use strict;
use warnings;

my @del_words = qw{is an to for from};
my $del_words_alt = join q{|} => @del_words;
my $del_re = qr{\b(?>$del_words_alt)\b\s*};

while (<>) {
    s{$del_re}{}g;
    print;
}
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Test run:

$ pm_string_array_del.pl
is that true
that true
this is from presentation
this presentation
to create
create
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