End of Life Ruby 3.1 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →

instance method

NilClass#=~

nil =~ other → nil

static VALUE
nil_match(VALUE obj1, VALUE obj2)
{
    return Qnil;
}

Dummy pattern matching – always returns nil.

See also #=== #^ #& #| also in 4.1 · 4.0 · 3.4 · 3.3 · 3.2 · 3.0