Function enter_stdin_repr 

pub fn enter_stdin_repr(repr: String) -> StdinReprGuard

Bind the representative PATH of the items arriving on stdin, for the duration of the guard — set by the pipeline walker to the previous stage’s output-path locus. An operand-injecting consumer (xargs) reads it so find / | xargs cat gates the injected operand at /, while find ./src | xargs cat gates it at the workspace (mirrors find -exec’s {} binding).