You say:

using this loop without knowing there is a pipeline will cause the program to hang till it gets an EOF on STDIN (which it obviously won't get).

Duh? This:

ls|perl -e 'while (<STDIN>) {/1/ and do{print}}'
[download]

works as expected (prints only the lines of the output of ls which contain a 1). OK, you need to do different processing in the case of a pipeline, but you will still get EOF.

Just nitpicking...

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        dakkar - Mobilis in mobile