protect $@ whenever a block using $@ is non-trivial

As noted in the Try::Tiny man page, eval/$@ can be quite awkward in
corner cases, because $@ has the same properties and problems as C's
errno. While writing a regression test for definetemplate
in which it couldn't find an appropriate template, I received

    <span class="error">Error: failed to process template
    <span class="createlink">deftmpl</span> </span>

instead of the intended

    <span class="error">Error: failed to process template
    <span class="createlink">deftmpl</span> template deftmpl not
    found</span>

which turned out to be because the "catch"-analogous block called
gettext before it used $@, and gettext can call define_gettext,
which uses eval.

This commit alters all current "catch"-like blocks that use $@, except
those that just do trivial things with $@ (string interpolation, string
concatenation) and call a function (die, error, print, etc.)

1 files changed, 2 insertions, 1 deletions

diff --git a/IkiWiki/Plugin/mdwn.pm b/IkiWiki/Plugin/mdwn.pm
index 430194bff..014e78eea 100644
--- a/IkiWiki/Plugin/mdwn.pm
+++ b/IkiWiki/Plugin/mdwn.pm
@@ -92,8 +92,9 @@ sub htmlize (@) {
 					$markdown_sub=\&Markdown::Markdown;
 				}
 				else {
+					my $error = $@;
 					do "/usr/bin/markdown" ||
-						error(sprintf(gettext("failed to load Markdown.pm perl module (%s) or /usr/bin/markdown (%s)"), $@, $!));
+						error(sprintf(gettext("failed to load Markdown.pm perl module (%s) or /usr/bin/markdown (%s)"), $error, $!));
 					$markdown_sub=\&Markdown::Markdown;
 				}
 			}