in reply to
Maybe Escape in Dynamic RegExps
This does what you want.
my $re = qr/(?<!\Q$c\E)\Q$d\E/;
The \Q . . \E pair is like quotemeta. I've changed the names to protect sort. Extra ( . . ) delimiter pair is cut.
Priority 1, Priority 2, Priority 3
Priority 1, Priority 0, Priority -1
Urgent, important, favour
Data loss, bug, enhancement
Out of scope, out of budget, out of line
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Impossible, inconceivable, implemented
Results (68 votes),