Do you want each sentence in a separate capture? Then the following would work:

my $test = do {local $/; <DATA>};

if ($test =~ m{((?:deferred|unrealized).*?\.)\s*(.*?\.)\s*(.*?\.)}s) {
    print "print '$1', '$2', '$3'";
}

__DATA__
foo bar. baz biz.
deferred gross profit is blah blah blah. more
blah.  and yet more blah.  But not this blah.
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Or if you don't care about them being separate, you could use the following

if ($test =~ m{(?=deferred|unrealized)((?:.*?\.){3})}s) {
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