Prefer scalar assignment to get caller's first return value

Multiple forms of syntax can be used to obtain a package name from
`caller`, which emits this as its first return value, and assign
that name to a lexical scalar.

The following each achieve the same result, but with varying efficiency:
* `sub callme { my $package = caller(2); ...}`
* `sub callme { my ($package) = caller(2); ...}`
* `sub callme { my $package = (caller(2))[0]; ...}`

In the first example, `pp_caller` determines only the package name
and pushes it to the stack. In the other two examples, the other 10 of
`caller`'s return values are calculated and pushed onto the stack,
before being discarded.

This commit changes non-CPAN-first instances of the latter two forms
in core to the first form.

Note: There is a special exception to the equivalence described above,
when caller is use in list context within the DB package. Such a
usage instance in regen/warnings.pl therefore remains unchanged.

1 files changed, 2 insertions, 2 deletions

diff --git a/regen/warnings.pl b/regen/warnings.pl
index 98e6b6cab9..21ee95d9b1 100644
--- a/regen/warnings.pl
+++ b/regen/warnings.pl
@@ -16,7 +16,7 @@
 #
 # This script is normally invoked from regen.pl.
 
-$VERSION = '1.62';
+$VERSION = '1.63';
 
 BEGIN {
     require './regen/regen_lib.pl';
@@ -849,7 +849,7 @@ sub __chk
             unless defined $offset;
     }
     else {
-        $category = (caller(1))[0] ;
+        $category = caller(1);
         $offset = $Offsets{$category};
         Croaker("package '$category' not registered for warnings")
             unless defined $offset ;