You can use capturing parentheses and a global match. Avoid using $&, $` and $' if you can as once used in a script they impose a performance penalty on all regular expressions in that script.

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

my @required = (
   q{this},
   q{that},
   q{the other},
   q{bat},
   );

my $rxRequired = do
   {
       local $" = q{|};
       qr{(?i)\b(@required)\b};
   };

my $text =
   q{This afternoon I found a bat in the other bath, that was odd!};

print for $text =~ m{$rxRequired}g;
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The output.

This
bat
the other
that
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I hope this is useful.

Cheers,

JohnGG