With either
    $string2 =~ /^h(.*)/o;
or
    $string2 =~ /^h(.*)/;
(i.e., either with or without the  /o regex modifier), I get the same results for ActiveState 5.8.9 and Strawberries 5.10.1 and 5.12.0 (all running under Windoze 7) and as I would expect (after a little thought) given the documented behavior of the  // empty regex:

>perl -wMstrict -le
"my @strings = ('testing','','testing','testing');
 foreach my $string (@strings) {
     print \"\nSTRING: $string\n\";
     my $string2 = 'http';
     $string2 =~ /^h(.*)/o;
     my $q = $string;
     my $test = 'testing';
     warn $test =~ /\Q$q\E/;
 }
"

STRING: testing

1 at -e line 1.

STRING:

Warning: something's wrong at -e line 1.

STRING: testing

1 at -e line 1.

STRING: testing

1 at -e line 1.
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