use strict;
my $str = 'Blah Blah Date Ordered: 5/19/2000 test is positive. Date Ordered: 4/2/2005 Additional testing negative.
Meh Date Ordered: 4/15/1999
irrelevant
--------------Date Ordered: 4/12/3456';
my $regex = qr~.*Date Ordered:\s*(\d{1,2}/\d{1,2}/\d{4}).*|.*~mp;
my $subst = '\\1';
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