匹配评估

如果匹配器找到至少一个匹配项，则求值为 true，如果未找到匹配则为 false

// a match is found => true
assert 'foo' =~ /[a-z]/
// the regexp does not match fully => no match => false
assert !( 'foo' ==~ /[a-z]/ )
// a match is found => true
assert 'foo' =~ /o/
// no match => false
assert !( 'foo' =~ /[A-Z]/ )