Thanks but this doesn't work for me. I know that qr returns a regex object, I was only using it because a straight substution doesn't do the trick. I don't have Path::Tiny so I amended your example: 
#!/usr/bin/perl -- 
use strict;
use warnings;
my $infile = 'C:\Scripts\Working2\Users_0.xml';
my $outfile = 'C:\Scripts\Working2\Users2.xml';
my $find = VerifyHex( '\xe9' );
my $replace = VerifyHex( '\x65' );
open(IF, "<$infile") or die "Could not open $infile $!";
open(OF, ">$outfile") or die "Could not open $outfile $!";
binmode IF;
binmode OF;
while( my $str = <IF> ){
      $str =~ s{$find}{$replace}g;
      print OF $str;
}
close IF;
close OF;
sub VerifyHex {
    my( $str ) = @_;
    if( $str =~ m/(\\[a-zA-Z0-9][a-zA-Z0-9])/ ){
        return "$1";
    }
    die "evil input $str";
}

[download]
The input file contains this (edited from an extract from an IBM tool), which says it's UTF-8 but isn't: 
<?xml version="1.0" encoding="UTF-8" ?>
<foundation Version="1.0.0">
    <contributor>
        <userId>C12760</userId>
        <name>Shilpaé Durgale</name>
    </contributor>
</foundation>

[download]
Sadly the output is unchanged from the input, the é is not replaced with e. As you can tell I'm no genius with Perl and I'm sure I'm missing something fundamental. Thoughts?

In reply to Re^2: Hex-matching Regex pattern in scalar ( substitution by CliffG
in thread Hex-matching Regex pattern in scalar by CliffG

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