Add s///r (non-destructive substitution).

This changes s/// so that it doesn't act destructively on its target.
Instead it returns the result of the substitution (or the original string if
there was no match).

In addition this patch:

  * Adds a new warning when s///r happens in void context.
  * Adds a error when you try to use s///r with !~
  * Makes it so constant strings can be bound to s///r with =~
  * Adds documentation.
  * Adds some tests.
  * Updates various debug code so it knows about the /r flag.
  * Adds some new 'r' words to B::Deparse.

1 files changed, 2 insertions, 0 deletions

diff --git a/op.h b/op.h
index 2109891c52..b9327bbb1f 100644
--- a/op.h
+++ b/op.h
@@ -376,6 +376,8 @@ struct pmop {
 #define PMf_GLOBAL	0x00002000	/* pattern had a g modifier */
 #define PMf_CONTINUE	0x00004000	/* don't reset pos() if //g fails */
 #define PMf_EVAL	0x00008000	/* evaluating replacement as expr */
+#define PMf_NONDESTRUCT	0x00010000	/* Return substituted string instead
+					   of modifying it. */
 
 /* The following flags have exact equivalents in regcomp.h with the prefix RXf_
  * which are stored in the regexp->extflags member. If you change them here,