Beautiful! Thanks for the quick response. It would have taken me weeks of trial and error to get to this point- but this helps me learn for next time. Much appreciated! Here is the final working code:

#!/usr/bin/perl -i.before_postproc

# Author  : David Sherwood
# Version : 1.0
# Copyright : none.
#
# Postprocessor for Slic3R Gcode for Laser Cutter

use strict;
use warnings;

# read stdin and any/all files passed as parameters one line at a time

while (<>) {
   
    chomp;    

    # EN.NNNNN 
    # no need for if(), we're not using the capture number vars

    s/E\d\.\d{5}//;
  
    # ZNN.NNN 
    # need if, or it'll warn on no match

    if (/G1 Z\d{1,2}\.\d{3}/){
        s/(G1 Z)(\d{1,2}\.\d{3})/$1-$2/;
           
    }           

    if (/G11/) {
        # if we have an un-retraction line, replace it with laser powe
+r on
        print "M400 ; wait for moves to finish\nM104 S100 ; laser on\n
+";
    }
    
    elsif (/G10/) {
        # if we found a retraction line, replace it with laser power o
+ff
        print "M104 S0 ; laser off\n";
    }
    
    elsif (/G92/) {
        # if we found an extruder reset command line, remove it
        print "";
    }
      
    elsif (/M190/) {
        # if we found a heat bed command line, remove it
        print "";
    }    
           
    else {
    print "$_\n" or die $!;
    }
}
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