If you copy the character and run something like this:

 perl -e 'print ord(shift) . "\n"' "’"
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You could match this with \x92

$in{'content'} =~ s/\x92/’/g;
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# Somewhere in an init function I define the hex value => string mappi
+ng
# I find it easier to edit this way
    my %seed = (
        '82' => ',',
        '83' => '<em>f</em>',
        '84' => ',,',
        '85' => '...',
        '88' => '^',
        '89' => ' °/°°',
        '8B' => '<',
        '8C' => 'Oe',
        '91' => '`',
        '92' => '\'',
        '93' => '"',
        '94' => '"',
        '95' => '*',
        '96' => '-',
        '97' => '--',
        '98' => '<sup>~</sup>',
        '99' => '<sup>TM</sup>',
        '9B' => '>',
        '9C' => 'oe',
    );
# Build a mapping of the hex code to string lookup table.
# I find it to be less error prone than maintaining it manually
    my %msword_replace = ();
    while (my ($hex, $replace_with) = each %seed) {
        $msword_replace{chr(hex($hex))} = $replace_with;
    }
    # Define a list of hex codes that will be used as the search patte
+rn
    # Then create a regex with alternation for these codes
    my @hex_codes = map {'\x' . $_} keys %seed;
    $msword_re = sprintf "(%s)", join('|', @hex_codes);

    # And then later when I need to do the replacing:
    $data =~ s/$msword_re/$msword_replace{$1}/g;
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Use a module or even CGI's escapeHTML() function perhaps.

I suspect that the ' character you're trying to substitute has a different ordinal value or encoding than the one actually contained in the string being acted upon. Could there be a character encoding issue here? I guess we need the actual input data and a little more of a snippet that reproduces the problem so as to provide a more definitive answer.

use HTML::Entities;
encode_entities($mystr);
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I agree. I think when the OP refers to "clean up" he may need decode_entities. It is worth noting that decode_entities returns utf8. It can bite you if you aren't expecting it.

My rule of thumb is either not decode (leave the HTML as it is) or (if your not otherwise working with utf8) do a manual conversion similar to what imp discusses above.

#!/usr/bin/perl

use strict;
use warnings;

use HTML::Entities;

print encode_entities(chr(0x92)), "\n";
print encode_entities(chr(0x2019)), "\n";
print sprintf '%02X', ord decode_entities('’');

__DATA__

’
’
2019
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update: Misread the question.