use strict;
my $str = 'Mr. Smith bought cheapsite.com for 1.5 million dollars, i.e. he paid a lot for it. Did he mind? Adam Jones Jr. thinks he didn\'t. In any case, this isn\'t true... Well, with a probability of .9 it isn\'t.';
my $regex = qr/(?<!\w\.\w.)(?<![A-Z][a-z]\.)(?<=\.|\?)\s/mp;
my $subst = '\\n';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html