❯ nextflow run main.nf
N E X T F L O W  ~  version 23.04.0
Launching `main.nf` [nostalgic_crick] DSL2 - revision: e660291f13
=============================================================================
=                                WARNING                                    =
= You are running this script using DSL2 syntax, however it does not        =
= contain any 'workflow' definition so there's nothing for Nextflow to run. =
=                                                                           =
= If this script was written using Nextflow DSL1 syntax, please add the     =
= setting 'nextflow.enable.dsl=1' to the nextflow.config file or use the    =
= command-line option '-dsl1' when running the pipeline.                    =
=                                                                           =
= More details at this link: https://www.nextflow.io/docs/latest/dsl2.html  =
=============================================================================

❯ nextflow run main.nf -dsl1
N E X T F L O W  ~  version 23.04.0
Nextflow DSL1 is no longer supported — Update your script to DSL2, or use Nextflow 22.10.x or earlier