How to efficiently search for list of strings in multiple files?

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my ( $first_match ) = grep { $line =~ m/\Q$_\E/ } keys %InputData_Empl
+oyersHash;
print $search and last SEARCH if $first_match ne "";

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read_in_data_union();
process_files ($FileFolder);
...
        }
    }
}

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Sarnia Employees' Bargaining Association
Sarnia Municipal Administrative Employees' Assn.
Sarnia Police Association
Sarnia Professional Fire Fighters'

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McMaster University

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