in reply to How to search and replace text characters in a perl script

Here's one example, kind of following along the code layout you already have. In the 'E' case, we simply attempt a regex substitution (s//;), and for the 'Z' entries, we check if we have a match first, capture the match into two parts ($1, $2), and if there is a match, we do the substitution:

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-$2/;
    }           
    print "$_\n";
}

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Re^2: How to search and replace text characters in a perl script
by AnomalousMonk (Archbishop) on May 20, 2016 at 06:11 UTC
    # need if, or it'll warn on no match

    No need: no substitution is done, no capture variables are referenced, if no replacement match exists: 

    c:\@Work\Perl\monks>perl -wMstrict -le
"for my $s ('G1 Z0.050 F7800.000',  'G10 ; retract',) {
   printf qq{'$s' -> };
   local $_ = $s;
   s/(G1 Z)(\d{1,2}\.\d{3})/$1-$2/;
   print qq{'$_'};
   }
"
'G1 Z0.050 F7800.000' -> 'G1 Z-0.050 F7800.000'
'G10 ; retract' -> 'G10 ; retract'

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    (Although I think I would prefer to use look-arounds as graff did and just stick a - in.)

    Give a man a fish:  <%-{-{-{-<

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Re^2: How to search and replace text characters in a perl script
by thetekguy (Initiate) on May 20, 2016 at 03:14 UTC
    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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