$shared .= <PIPE>;

##</code><code>##

    my $local = <PIPE>;
    $shared .= $local; 

##</code><code>##

    my $local = <PIPE>;
    { lock( $shared ); $shared = $local; }

##</code><code>##

{ 
    lock( $shared );
    my $local = <PIPE>;
    $shared = $local; 
}

##</code><code>##

# XXX. The key and value are related.
my $string = $shared_key . ' => ' . $shared_value;

##</code><code>##

C:\test>perl -MO=Terse
my $string = $shared_key . ' => ' . $shared_value;
^Z
LISTOP (0x191d964) leave [1]
    OP (0x191d948) enter
    COP (0x191d988) nextstate
    ## exception handler installed here!
    BINOP (0x191d9c4) sassign
    ## exception handler entered here and the entire subtree retried <<<------+
    ## critical section entered here (on second attempt)                      |
        BINOP (0x191d9e8) concat [5]                                          |
            BINOP (0x191da4c) concat [3]                                      |
                UNOP (0x191da90) null [15]                                    |
                    PADOP (0x191dab0) gvsv  GV (0x182435c) *shared_key        |
                    ## Exception triggered here by the access to shared data.-+
                SVOP (0x191da70) const [6] PV (0x1824374) " => "
            UNOP (0x191da0c) null [15]
                PADOP (0x191da2c) gvsv  GV (0x18243b0) *shared_value
        OP (0x191dad0) padsv [1]
    ## critical section exited here.
- syntax OK

##</code><code>##

{
    lock( $shared )
    $local = $shared;
    $shared = somefunction( $local );
}

##</code><code>##

$shared = somefunction( $shared );

##</code><code>##

C:\test>perl -MO=Terse
sub somefunction{ $_[0] + 1 }

$shared = somefunction( $shared );
^Z
LISTOP (0x191d7e0) leave [1]
    OP (0x191d7c4) enter
    COP (0x191d804) nextstate
    ## install exception handler here
    BINOP (0x191d840) sassign
    ## Exception handler catches here <<<<---------------------------^
    ## Critical section entered here at second attempt
        UNOP (0x191d864) entersub [4]
            UNOP (0x191d8a0) null [141]
                OP (0x191d884) pushmark
                UNOP (0x191d8c4) null [15]
                    PADOP (0x191d8e4) gvsv  GV (0x22507c) *shared
                    ## Exception raised here---------------------------^
                UNOP (0x191d904) null [17]
                    PADOP (0x191d924) gv  GV (0x225088) *somefunction
        UNOP (0x191d944) null [15]
            PADOP (0x191d964) gvsv  GV (0x22507c) *shared
    ## ExitCriticalSection here.
- syntax OK