#!/usr/bin/perl
use strict;
use warnings;

my $input  = 'infile.txt' ;
my $output = 'outfile.txt';

my $t0 = time();
open my $in_fh, '<', $input or die "Can't open $input: $!";
open my $out_fh, '>', $output or die "Can't open $output: $!";

my $s = 1234;
my @id = (); my $count = 0;

while (my $line = <$in_fh>){
  my @pos = ();
  while ($line =~ m/([»«›‹])/g) {
    my $q = $1;
    if ($q =~ /[»›]/){
      push @pos,[pos($line),qq{<q marker="$q" sID="$s"\/>}];    
      push @id,$s++
    } else {
      my $e = pop @id;
      push @pos,[pos($line),qq{<q marker="$q" eID="$e"\/>}];          
    }
  }
  
  # reverse to preserve positions after replacement
  for (reverse @pos){
    substr($line,$_->[0]-1,1) = $_->[1];  
  }
  
  print $out_fh $line;
  ++$count;
}

close $in_fh or die $!;
close $out_fh or die $!;

my $dur = $t0-time();
print "$count lines processed in $dur seconds\n";