my %filehandle_of;
foreach my $filename (@filenames) {

    # here $filehandle is a reference to a new anonymous filehandle in each iteration, you can push it into an array if you don't need the mapping instead
    if (open my $filehandle, '<', $filename) {

        $filehandle_of{$filename} = $filehandle;

    } else {

        warn "could not open '$filename' for reading: $!\n";
        next;

    }

}