params.str = "Hello world" 

// Renamed from 'split' to 'split_text' to avoid Groovy method name conflict
process split_text {
    input:
    val x

    output:
    path 'chunk_*'

    script:
    """
    printf '${x}' | split -b 6 - chunk_
    """
}

process convert_to_upper {
    input:
    path y

    output:
    path 'upper_*'

    script:
    """
    cat $y | tr '[a-z]' '[A-Z]' > upper_${y}
    """
}

workflow {
    main:
    ch_str = channel.of(params.str)
    ch_chunks = split_text(ch_str)
}