I'd suggest that you start with one string at a time until you know more about what you are trying to do. List::AllUtils would be a good place to start. "delete" is trivial, so I leave that to you.

#!/usr/bin/perl 

use autodie;
use strict qw/refs/;
use warnings FATAL => 'all';
use List::AllUtils qw/:all/;

my (@arr) = qw( is an to for from );

my $str1 = ("This is not true");
    print "At least one value is undefined\n"
        if all sub {  
            defined $_ 
        },  @arr;
printf "\t %i item(s) is(are) defined  ", true { defined $_ } $str1;
print "\n";
print  "\t The defined element is: before_incl { defined $_ } @arr";
print "\n";
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