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

In reply to Re^3: performing operation on elements not in list? by johngg
in thread performing operation on elements not in list? by Anonymous Monk

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