It uses <...> in its file-globbing context. This means any elements in @array that contain wildcard characters for your shell will be expanded into all matching filenames. It also means that if any of your elements have whitespace in them, they'll be split on that whitespace.

@array = ("this", "is not", "cool");
print "[$_]" while <@array>;  # [this][is][not][cool]
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It's misuse of an operator, and I'm irked that Perl lets it fly without even alerting you to the potential gaffe you're making.