Block Structure

$try
 .. risky commands...
$catch
 .. recovery commands...
$endTry

1. The parser executes the body between $try and $catch.
2. If no error occurs, the $catch block is skipped entirely and execution resumes after $endTry.
3. If any function error occurs inside the $try body, execution immediately jumps to $catch. The error is consumed — it will not propagate outside the try-catch. An error raised inside the $catch block itself is not caught by that same $try. $catch is optional: without it, an error in the body is swallowed and execution resumes after $endTry.

Important: $endTry is always required, even if no $catch is provided.

The $error Variable

Inside the $catch block, the $error variable provides access to the caught error’s metadata:

Usage	Returns
$error	The full error text (with a BDFD location prefix of the form BDFD L<line>:<column> $function: ...)
$error[message]	The error message alone, without the location prefix
$error[command]	The name of the command that caused the error
$error[source]	The source line or context of the error
$error[row]	The row number where the error occurred
$error[column]	The column number where the error occurred

Any other type (the types are lowercase) raises the error Error type must be command, message, source, row or column. $error is empty until an error has been caught; it is meant to be used within the $catch block. The recorded values are not cleared when the block ends.

Nesting

$try blocks can be nested. Each $catch only catches errors from its own $try body. An error caught in an inner $catch does not propagate to an outer $catch.

Interaction with $stop

If $stop is called inside a $try block, it halts execution before the $catch is reached — so the error handler does not run. This is by design: $stop is an unconditional halt.

Use Cases

• API calls: Wrap $httpGet / $httpPost calls to handle network failures.
• User input parsing: Catch errors when parsing or coercing user-supplied values.
• Fallback logic: Try a primary operation, fall back to a secondary on failure.
• Logging: Use $catch to log errors with $log[] or save them to a variable for later inspection.

Common Pitfalls

• Forgetting $endTry produces a parse error (“Missing $endtry.”).
• Placing $endTry before $catch — the parser expects $catch before $endTry.
• Using $error outside $catch — it only holds a value once an error has been caught.
• Using arguments on the delimiters — $catch and $endTry accept none, and a $try with arguments is not a block.
• Catching an error but doing nothing with it — at minimum, log it to help with debugging.

Examples

Error-Protected Expression Evaluation

$try
  $var[result;$calculate[$message]]
  $title[Calculation Succeeded]
  $description[Result: **$var[result]**]
  $color[#57F287]
$catch
  $title[Calculation Failed]
  $description[Invalid mathematical expression provided!]
  $color[#ED4245]
$endTry
$sendMessage[Calculation processed]