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.)