error.xgml

<Library name="error-lib">
<item id="catch-all" exec="1"><![CDATA[
dict begin
/_on-catch edef
/_try edef
{
  {
    _try
  } {
    /_error
    throw
  } catch-error
} {
  count 1 gt {
    exch dup /_error eq {
      2 pops
    } {
      exch
    } ifelse
  } if
  _on-catch
} catch
end
]]></item>
</Library>