Make readpipe default to $_

p4raw-id: //depot/perl@30747

3 files changed, 14 insertions, 2 deletions

diff --git a/op.c b/op.c
index c10bf952ac..48437cfccb 100644
--- a/op.c
+++ b/op.c
@@ -6908,8 +6908,13 @@ Perl_ck_open(pTHX_ OP *o)
 		o->op_private |= OPpOPEN_OUT_CRLF;
 	}
     }
-    if (o->op_type == OP_BACKTICK)
+    if (o->op_type == OP_BACKTICK) {
+	if (!(o->op_flags & OPf_KIDS)) {
+	    op_free(o);
+	    return newUNOP(OP_BACKTICK, 0, newDEFSVOP());
+	}
 	return o;
+    }
     {
 	 /* In case of three-arg dup open remove strictness
 	  * from the last arg if it is a bareword. */
diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod
index c23dbd9af5..ab0213636c 100644
--- a/pod/perlfunc.pod
+++ b/pod/perlfunc.pod
@@ -4305,6 +4305,8 @@ error, returns the undefined value and sets C<$!> (errno).  If EXPR is
 omitted, uses C<$_>.
 
 =item readpipe EXPR
+
+=item readpipe
 X<readpipe>
 
 EXPR is executed as a system command.
@@ -4315,6 +4317,7 @@ multi-line) string.  In list context, returns a list of lines
 This is the internal function implementing the C<qx/EXPR/>
 operator, but you can use it directly.  The C<qx/EXPR/>
 operator is discussed in more detail in L<perlop/"I/O Operators">.
+If EXPR is omitted, uses C<$_>.
 
 =item recv SOCKET,SCALAR,LENGTH,FLAGS
 X<recv>
diff --git a/t/op/exec.t b/t/op/exec.t
index c13849199a..ed5b2b6116 100755
--- a/t/op/exec.t
+++ b/t/op/exec.t
@@ -19,7 +19,7 @@ my $Is_Win32 = $^O eq 'MSWin32';
 
 skip_all("Tests mostly usesless on MacOS") if $^O eq 'MacOS';
 
-plan(tests => 21);
+plan(tests => 22);
 
 my $Perl = which_perl();
 
@@ -106,6 +106,10 @@ is( <<`END`,                    "ok\n",     '<<`HEREDOC`' );
 $Perl -le "print 'ok'"
 END
 
+{
+    my $_ = qq($Perl -le "print 'ok'");
+    is( readpipe, "ok\n", 'readpipe default argument' );
+}
 
 TODO: {
     my $tnum = curr_test();