my @dispatch = ( { pattern => qr/DNI/,
                   coderef => \&do_dni, },
                 { pattern => qr/SNI/,
                   coderef => \&do_sni, },
                );
foreach my $fn ( @filenames ) {
    foreach my $item ( @dispatch ) {
        $item->{coderef}->($fn)
            if ( $fn =~ $item->{pattern} );
    }
}