匹配評估

如果匹配器找到至少一個匹配項，則求值為 true，如果未找到匹配則為 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]/ )