Re^2: performing operation on elements not in list?

Two errors.

You end up with qr/^two|three$/ which matches "twoo".
You don't convert the keys to regexp

If the list of keys to keep is static, you want

my $inv = qr/two|three/;
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If the list of keys to keep is dynamic, you want

my $inv = do{ local $" = q{|}; qr{@{[ map quotemeta, @keep ]}} };
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or the much simpler

my ($inv) = map qr/$_/, join '|', map quotemeta, @keep;
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In all cases, use /^$inv\z/ in the grep.

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Re^3: performing operation on elements not in list? by johngg (Canon) on Jan 09, 2009 at 22:03 UTC
Good catch regarding the anchors and alternation. The OP says "given the same ... list" so the keys not to change are invariable. So I should have said. `$inv = do{ local $" = q{\|}; qr{^(?:@{ [ qw{ two three } ] })$} };` [download] I'm not sure what you mean when you say I don't convert the keys to regexp. Cheers, JohnGG	[reply] [d/l]
Re^4: performing operation on elements not in list? by ikegami (Patriarch) on Jan 09, 2009 at 22:13 UTC
So I should have said. No, that's insanely complex for a static pattern. Also, I prefer to put the anchors in the parent regexp. It makes more sense conceptually, the code pattern work in more situations, and you don't have to add `(?:)` since `qr//` adds one for you. I'm not sure what you mean when you say I don't convert the keys to regexp. Injection bug. See the addition of `quotemeta` in the last two snippets.	[reply] [d/l] [select]
Re^4: performing operation on elements not in list? by ikegami (Patriarch) on Jan 09, 2009 at 22:15 UTC
So I should have said. No, that's insanely complex for a static pattern. Also, I prefer to put the anchors in the parent regexp. It makes more sense conceptually, the code pattern work in more situations, and you don't have to add `(?:)` since `qr//` adds one for you. I'm not sure what you mean when you say I don't convert the keys to regexp. Injection bug. See the addition of `quotemeta` in the last two snippets.	[reply] [d/l] [select]