eq is the string comparison operator. It compares strings. It therefore needs strings. If you pass it something that isn't a string, it's coerced into a string. In the case of undef, that means an empty string, but you get a warning for doing this.

You want «defined($y) && !length($y)» or «defined($y) && $y eq ''».

In reply to Re: defined vs null string by ikegami
in thread defined vs null string by Anonymous Monk

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