my $foo  = "A man and a woman saw a frog by the pond\n";

s/frog/toad/g, s/man/boy/, s/woman/girl/, print for ($foo);

__END__
A boy and a girl saw a toad by the pond


##</code><code>##

s/\bfrog\b/toad/g, s/\bman\b/boy/, s/\bwoman\b/girl/, print for $foo;