Since you mentioned DFA with regex (which reminded me of natural language processing), here's a naive twisted example: 
use Tie::RegexpHash;
use Regexp::Subst::Parallel;
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
my $how = sub {
    my %ans = (
        is => "print \"It's fine.\\n\"",
        are => "howare(\"$_[3]\")"
    );
    eval $ans{$_[2]} ;
};

sub howare {
    tie my %ans, 'Tie::RegexpHash';
    %ans = (
        qr/you/i           => "print \"I'm fine.\\n\"",
        qr/^(?!you)(.*)$/i => "print \"All good.\\n\""
    );    
    eval $ans{$_[0]} ;
}
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
my @sr =(      
    qr/^(how) (is|are) (you|.*)(\?)$/i => $how,
    qr/^(?!how)(.*)$/i                 => sub{print "Say what?\n"}
);
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
$_ = "\nHow is everything?\n"; print; 
subst($_, @sr);

$_ = "\nHow are you?\n"; print; 
subst($_, @sr);

$_ = "\nHow are things?\n"; print; 
subst($_, @sr);

$_ = "\nDo you dig me?\n"; print; 
subst($_, @sr);


__END__

How is everything?
It's fine.

How are you?
I'm fine.

How are things?
All good.

Do you dig me?
Say what?

[download]

In reply to Re: Re: 3 Examples of Multiple-Word Search n Replace by chunlou
in thread 3 Examples of Multiple-Word Search n Replace by chunlou

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.