It's not a feature or bug, it just is :)

defined() returns a bool, (either false/true) when it evaluates something, so when you do this: defined ($x || $y);, it's not doing what you think it does.

Here's an example that illustrates the issue:

perl -wMstrict -E 'my $x = defined $ARGV[5]; say defined $x'
1

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Now, $ARGV[5] is not set in any way, but since we're returning the value of the call to $x, $x will most definitely be defined, because it now evaluates to false as the variable was not defined (define() returns false, if something wasn't defined).

You need to call a define on each side of the comparison operator:

my $x = defined $x || defined $y;

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...as per your solutions that work. Then, check $x for truth:

die "blah...\n" if ! $x;

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...or combined:

die "blech...\n" if ! defined $x || defined $y;

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In reply to Re: "defined" function fails to evaluate expression; feature or fault? by stevieb
in thread "defined" function fails to evaluate expression; feature or fault? by w8lle

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