It's easier to see the diff here: 
$ diff -u \
    <( perl -MO=Concise,-exec -e'@vals = map   $_*5,  @vals;' 2>&1 ) \
    <( perl -MO=Concise,-exec -e'@vals = map { $_*5 } @vals;' 2>&1 )
--- /proc/self/fd/63    2010-01-24 01:45:47.147224485 -0800
+++ /proc/self/fd/62    2010-01-24 01:45:47.123224005 -0800
@@ -1,18 +1,19 @@
 -e syntax OK
 1  <0> enter
-2  <;> nextstate(main 1 -e:1) v
+2  <;> nextstate(main 2 -e:1) v
 3  <0> pushmark s
 4  <0> pushmark s
 5  <#> gv[*vals] s
 6  <1> rv2av[t6] lKM/1
-7  <@> mapstart lK/2
-8  <|> mapwhile(other->9)[t7] lK/1
+7  <@> mapstart lK*/2
+8  <|> mapwhile(other->9)[t8] lK/1
 9      <#> gvsv[*_] s
 a      <$> const[IV 5] s
 b      <2> multiply[t4] sK/2
+-      <@> scope lK
            goto 8
 c  <0> pushmark s
 d  <#> gv[*vals] s
 e  <1> rv2av[t2] lKRM*/1
-f  <2> aassign[t8] vKS/COMMON
+f  <2> aassign[t9] vKS/COMMON
 g  <@> leave[1 ref] vKP/REFC

[download]

It's very unclear what that means. The leading "-" means it's not executed, yet it's still showing in the -exec listing. What does that OP do anyway? It's executed at the *end* of the callback code. Looking at the source doesn't help 

PP(pp_scope)
{
    dVAR;
    return NORMAL;
}

[download]

Without a lot more digging, B::Concise's output does really help. On the other hand, it's very easy to show that a scope does get created for map BLOCK but not for map EXPR,

...or not. 

$ perl -wle'use strict; map +(my $x = $_), 2; print $x'
Use of uninitialized value in print at -e line 1.

[download]

It seems a run-time scope is created for map EXPR,.

(Compile-time scope affects the visibility of lexical variables. Run-time scopes control when they get cleared. They should be the same, but sometimes they're not.)

In reply to Re^2: syntax of map operator by ikegami
in thread syntax of map operator by sman

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