什么是灵丹妙药中的=〜运算符

Question

From the documentation I understand how =~ operator works to match regex, but I don't understand the general use of this operator.

For example, what does "foo" =~ "foo" mean? How is it different from "foo" == "foo" ?

Answer 1

It's not documented on that page, but it's documented in Kernel.=~/2 that when the RHS is a string, =~ checks if LHS contains RHS:

iex(1)> "foo" =~ "f"
true
iex(2)> "foo" =~ "o"
true

It does not implicitly convert RHS to regex:

iex(3)> "foo" =~ "."
false