How do I iterate over nth files from within a process?

[DescartesM]

https://www.nextflow.io/docs/latest/faq.html?highlight=loop#how-do-i-iterate-over-nth-files-from-within-a-process

I found an example on the FAQ, but it not work for me. Maybe I made some mistakes.
here is my nf file, and I get the error

 Apr-01 14:25:07.218 [main] ERROR nextflow.cli.Launcher - @unknown 
 groovy.lang.MissingPropertyException: Unknown variable 'in_ch' 
 	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
 	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) 
 	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) 
 	at java.base/java.lang.reflect.Constructor.newInstance(Unknown Source) 

#!/usr/bin/env nextflow
nextflow.enable.dsl=2
process copy_data_for_loop {
  input:
    path inList from in_ch.collect()
  output:
    path('*.txt')

  script:
  """
  for inElem in ${inList}
  do
       cp ${inElem} new-${inElem}.txt;
       echo ${inElem};
  done
  """
}
workflow {
  in_ch = Channel.fromPath(params.in)
  outputs = copy_data_for_loop(in_ch)
}

Then I change my nf file, get the different error

 Caused by: 
   No such variable: inElem -- Check script data-copy-loop' at line: 11 
  
 Source block: 
   """ 
     for inElem in ${inList} 
     do 
          cp ${inElem} new-${inElem}.txt; 
          echo ${inElem}; 
     done 
     """ 

#!/usr/bin/env nextflow
nextflow.enable.dsl=2

process copy_data_for_loop {
  input:
    path inList
  output:
    path('*.txt')

  script:
  """
  for inElem in ${inList}
  do
       cp ${inElem} new-${inElem}.txt;
       echo ${inElem};
  done
  """
}

workflow {
  in_ch = Channel.fromPath(params.in).collect()
  outputs = copy_data_for_loop(in_ch)
}

[bentsherman]

That FAQ is very out of date, it will be removed soon. The example you copied was in DSL1, but I see you ported it to DSL2.

Your current error is that inElem is a Bash variable, not a Nextflow variable, so you need to escape it in the script: \${inElem}.