Replaces repeated variables in a pattern with _, removing the equality constraint created by the repetition:

def equal?(x, x), do: true  →  def equal?(_, _), do: true

The replacement policy keeps required bindings intact:

• If the variable is read by the guard or body, or appears at least three times in the head, one mutant is produced for each wildcarded occurrence.
• If it appears exactly twice and is not read elsewhere, both occurrences are replaced in one mutant. Replacing only one would leave an unused binding.

_, underscore-prefixed names, pinned variables, and module-attribute reads (%{@key => v} — a compile-time constant whose inner AST merely looks like a variable) are not counted or replaced. On the right side of a bitstring ::, atoms such as binary have the same AST shape as variables, so that side is not searched for pattern occurrences.

A variable read by a bitstring specifier is also excluded. For example, the n bound and read by <<n, rest::size(n)>> cannot be wildcarded without leaving an invalid size reference.

This family is enabled by default and uses the pattern_wildcard ignore name.