make qr/(?{})/ behave with closures

With this commit, qr// with a literal (compile-time) code block
will Do the Right Thing as regards closures and the scope of lexical vars;
in particular, the following now creates three regexes that match 1, 2
and 3:

    for my $i (0..2) {
        push @r, qr/^(??{$i})$/;
    }
    "1" =~ $r[1]; # matches

Previously, $i would be evaluated as undef in all 3 patterns.

This is achieved by wrapping the compilation of the pattern within a
new anonymous CV, which is then attached to the pattern. At run-time
pp_qr() clones the CV as well as copying the REGEXP; and when the code
block is executed, it does so using the pad of the cloned CV.
Which makes everything come out all right in the wash.

The CV is stored in a new field of the REGEXP, called qr_anoncv.

Note that run-time qr//s are still not fixed, e.g. qr/$foo(?{...})/;
nor is it yet fixed where the qr// is embedded within another pattern:
continuing with the code example from above,

    my $i = 99;
    "1"   =~ $r[1];    # bare qr:     matches: correct!
    "X99" =~ /X$r[1]/; # embedded qr: matches: whoops, it's still
					       seeing the wrong $i

2 files changed, 7 insertions, 9 deletions

diff --git a/t/lib/strict/subs b/t/lib/strict/subs
index e3e401408f..5fd0b03de7 100644
--- a/t/lib/strict/subs
+++ b/t/lib/strict/subs
@@ -378,8 +378,8 @@ Execution of - aborted due to compilation errors.
 use strict 'subs';
 qr/(?{my $x=foo})/;
 EXPECT
-Bareword "foo" not allowed while "strict subs" in use at (re_eval 1) line 1.
-Compilation failed in regexp at - line 3.
+Bareword "foo" not allowed while "strict subs" in use at - line 3.
+Execution of - aborted due to compilation errors.
 ########
 # Regexp compilation errors weren't UTF-8 clean
 use strict 'subs';
@@ -387,8 +387,8 @@ use utf8;
 use open qw( :utf8 :std );
 qr/(?{my $x=fòò})/;
 EXPECT
-Bareword "fòò" not allowed while "strict subs" in use at (re_eval 1) line 1.
-Compilation failed in regexp at - line 5.
+Bareword "fòò" not allowed while "strict subs" in use at - line 5.
+Execution of - aborted due to compilation errors.
 ########
 #  [perl #27628] strict 'subs' didn't warn on bareword array index
 use strict 'subs';
diff --git a/t/lib/strict/vars b/t/lib/strict/vars
index 6e3c1e90f4..c6cb067939 100644
--- a/t/lib/strict/vars
+++ b/t/lib/strict/vars
@@ -517,11 +517,9 @@ Execution of - aborted due to compilation errors.
 # [perl #26910] hints not propagated into (?{...})
 use strict 'vars';
 qr/(?{$foo++})/;
-# XXX temp expect duplicate errors
 EXPECT
 Global symbol "$foo" requires explicit package name at - line 3.
-Global symbol "$foo" requires explicit package name at (re_eval 1) line 1.
-Compilation failed in regexp at - line 3.
+Execution of - aborted due to compilation errors.
 ########
 # Regex compilation errors weren't UTF-8 clean.
 use strict 'vars';
@@ -529,8 +527,8 @@ use utf8;
 use open qw( :utf8 :std );
 qr/(?{$fòò++})/;
 EXPECT
-Global symbol "$fòò" requires explicit package name at (re_eval 1) line 1.
-Compilation failed in regexp at - line 5.
+Global symbol "$fòò" requires explicit package name at - line 5.
+Execution of - aborted due to compilation errors.
 ########
 # [perl #73712] 'Variable is not imported' should be suppressible
 $dweck;