1 while ....

That makes sense. Thanks.

NB - the 1 in a require isn't evaluated in a void context...

It is if, as I wrote, you syntax-check I did not write about the normal situation in which a module is require-ed; I referred to the case when one syntax-checks the module's file with perl -wc, e.g.:

% echo 1 > Foo.pm
% perl -wc Foo.pm
Foo.pm syntax OK
% echo 2 > Foo.pm
% perl -wc Foo.pm 
Useless use of a constant in void context at Foo.pm line 1.
Foo.pm syntax OK
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But yes, normally, when a module is require'd the 1 (or whatever) is not evaluated in a void context.

Update: I fixed the wording, in response to ikegami's reply. The question of whether doing a syntax check on a module with perl -wc somehow turns it into a script is too metaphysical even for me.