Note that the implicit "$_ = " in a while/until expression is only added for <>, readline, or glob operations.

There's an implicit defined() also, as ikegami notes, but that's broader. It is added when the while/until condition is a scalar assignment (itself possibly implicit as noted above) from a <>, readline, glob, readdir, or each operation.

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In reply to Re^2: <STDIN> not initializing $_ by ysth
in thread <STDIN> not initializing $_ by carol

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