Regina Rexx 4.00 STREAM default changed to APPEND: making retry writes idempotent across interpreters

Retry-safe file writes after the Regina 4.00 STREAM default change

I maintain REXX scripts that run under both Regina Rexx and IBM Object REXX for Windows. The scripts use a programmer-written retry loop around output operations: if a write fails, the loop re-executes the same LINEOUT call against the same stream.

Regina Rexx 4.00 introduced a configurable STREAM default mode (APPEND versus REPLACE), while IBM Object REXX keeps the historic REPLACE default unless APPEND is passed explicitly on the STREAM call. This means the same retry loop can silently duplicate lines on one interpreter and overwrite prior content on another, depending on the version and configuration in effect.

The REXX language standard does not define a retry mechanism, so the loop is my own code and currently does not distinguish transient failures from permanent ones. I want one portable script that produces identical file contents regardless of interpreter, without assuming a particular STREAM default.

My questions:

1. Is the Regina 4.00 STREAM default mode configurable per-script (for example via an option or environment setting), or only at interpreter build/install level?
2. What is the recommended portable pattern for making a retried LINEOUT idempotent when the default mode may be either APPEND or REPLACE?
3. Can a script reliably detect the active default at runtime (beyond parsing VERSION()) to branch its write logic?