reg_path_only

#!/usr/bin/perl

# use case: accept a UTF-16LE .reg file for "all environment variables" and remove all variables/values except for "Path"

# oh the humanity!!!  http://blogs.perl.org/users/yary/2016/01/utf-16-and-windows-crlf-oh-my.html
# oh the insanity!!!  http://blogs.perl.org/users/yary/2016/01/utf-16-and-windows-crlf-oh-my.html
# this solution violates
#   use strict;
#   use warnings;
# so both must be removed.

# NB!!!!! input .reg file MUST be passed via STDIN!!!  If you pass a filename, this program will not error out, but will write UNENCODED (invalid) output
# NB!!!!! input .reg file MUST be passed via STDIN!!!  If you pass a filename, this program will not error out, but will write UNENCODED (invalid) output
# NB!!!!! input .reg file MUST be passed via STDIN!!!  If you pass a filename, this program will not error out, but will write UNENCODED (invalid) output

my $varnm = shift @ARGV // "Path";
print STDERR "varnm $varnm\n";

binmode($_,':raw:encoding(UTF-16LE):crlf') for(STDIN,STDOUT);

my $q2 = '"';
while ( <> ) {
   if( $. <= 3 ) {  # first 3 lines of .reg file are necessary boilerplate
      print;
      next;
      }
   if( /^\Q${q2}${varnm}${q2}/io .. not /[0-9a-f]{2},\\$/ ) {
      print;
      next;
      }
   }