Another place where using 1 in void context is commonplace is near/at the end of modules. When use Foo loads Foo.pm, then the last expression evaluated inside Foo.pm better be a true value, to signal that the module loaded succesfully. That's why you usually see the line

1;
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near or at the end of a .pm file. Because 1 evaluates to a true value, but is special-cased not to raise a warning.