use strict;
use warnings;

use Data::Dumper;

open my $dictFH, q{<}, \ <<'DICT' or die qq{open: < HEREDOC: $!\n};
1 eat
2 habit
3 boy
4 man-kind
5 man
6 kind
7 bar
8 graph
9 bar graph
DICT

my %dict = reverse
   map { split m{\s+}, $_, 2 }
   map { chomp; $_ }
   <$dictFH>;

close $dictFH or die qq{close: < HEREDOC: $!\n};

print Data::Dumper->Dumpxs( [  \ %dict ], [ qw{ *dict } ] );

my $text = <<'TEXT';
The boy has a habit of eating kind of like a man.  Man-kind, as
a group, does not wear habits.  Kind of you to watch what you
eat. Make a bar graph of what drinks are drunk in a bar and the
graph could be coloured in.
TEXT

my $rxDict = do {
   local $" = q{|};
   qr
   {(?xi)
       \b(
       @{ [ map quotemeta, sort { $b cmp $a } keys %dict ] }
       )\b
   }
   };

$text =~ s{$rxDict}{ $dict{ lc $1 } }eg;
print $text;

##</code><code>##

%dict = (
          'eat' => '1',
          'man' => '5',
          'kind' => '6',
          'bar' => '7',
          'man-kind' => '4',
          'bar graph' => '9',
          'boy' => '3',
          'graph' => '8',
          'habit' => '2'
        );
The 3 has a 2 of eating 6 of like a 5.  4, as
a group, does not wear habits.  6 of you to watch what you
1. Make a 9 of what drinks are drunk in a 7 and the
8 could be coloured in.

##</code><code>##

The 3 has a 2 of eating 6 of like a 5.  5-6, as
a group, does not wear habits.  6 of you to watch what you
1. Make a 7 8 of what drinks are drunk in a 7 and the
8 could be coloured in.