Restore the value of $@ from before the local

[p5sagit/Try-Tiny.git] / lib / Try / Tiny.pm

diff --git a/lib/Try/Tiny.pm b/lib/Try/Tiny.pm
index dd6d466..e3fdf8d 100644 (file)
--- a/lib/Try/Tiny.pm
+++ b/lib/Try/Tiny.pm
@@ -23,6 +23,9 @@ sub try (&;$) {
        # to $failed
        my $wantarray = wantarray;
 
+       # save the value of $@ so we can set $@ back to it in the begining of the eval
+       my $prev_error = $@;
+
        my ( @ret, $error, $failed );
 
        # FIXME consider using local $SIG{__DIE__} to accumilate all errors. It's
@@ -37,6 +40,7 @@ sub try (&;$) {
                # failed will be true if the eval dies, because 1 will not be returned
                # from the eval body
                $failed = not eval {
+                       $@ = $prev_error;
 
                        # evaluate the try block in the correct context
                        if ( $wantarray ) {
@@ -180,6 +184,13 @@ not yet handled.
 C<$@> must be properly localized before invoking C<eval> in order to avoid this
 issue.
 
+More specifically, C<$@> is clobbered at the begining of the C<eval>, which
+also makes it impossible to capture the previous error before you die (for
+instance when making exception objects with error stacks).
+
+For this reason C<try> will actually set C<$@> to its previous value (before
+the localization) in the begining of the C<eval> block.
+
 =head2 Localizing $@ silently masks errors
 
 Inside an eval block C<die> behaves sort of like: