my %k;
$k{'A'} = 'Foo';
$k{'B'} = 'Bar';
$k{'C'} = 'Baz';

##</code><code>##

s/@k{qw(A B C)}/stuff/;

##</code><code>##

s/Foo Bar Baz/stuff/;

##</code><code>##

s/FooBarBaz/stuff;

##</code><code>##

print @k{qw(A B C)}, $/;

##</code><code>##

$x = join('', @k{qw(A B C)});
s/$x/stuff/;