# Keep around:
my $string = "Sat, 05 Jan 2013 04:00:15 GMT";
my ($match) = $string =~ m/(\d{2} [A-Z][a-z]{2} \d+)/;
print "Take out and keep: <$match> found in <$string>\n";
# Output: Take out and keep: <05 Jan 2013> found in <Sat, 05 Jan 2013 04:00:15 GMT>