my_input_files = Channel.fromPath( './data/*.txt' )

process doSomething {

    label (params.GPU == "ON" ? 'with_gpus': 'with_cpus')

    input:
    set file(inputfile) from my_input_files

    output:
    set file("${inputfile}.out") into my_output_files

    script:
    """
    echo "my wonderful ${inputfile} > ${inputfile}.out"
    """
}