How do I do a case-insensitive replace all for a string?

The option to replace case insensitive regex in java is Pattern.CASE_INSENSITIVE, which can also be specified as (?i)

(http://boards.developerforce.com/t5/Apex-Code-Development/Why-Pattern-CASE-INSENSITIVE-not-detectable/td-p/204337)

String srcStr = '{!id} value {!Id} is not {!ID}';
String replaceToken = '(?i)\\{!id\\}';
System.debug('REPLACEMENT ' + srcStr.replaceAll(replaceToken, ''));
System.assertEquals('  value  is not ', srcStr.replaceAll(replaceToken, ''));

Just curious can you not convert the string to a particular case?

say

String ex = 'Upper';
ex.toLowerCase();

(or)

ex.toUpperCase()

Examples from the official documentation -

String s1 = 'ThIs iS hArD tO rEaD';
System.assertEquals('this is hard to read',
s1.toLowerCase());

String myString1 = 'abcd';
String myString2 = 'ABCD';
myString1 = 
   myString1.toUpperCase();
Boolean result = 
   myString1.equals(myString2);
System.assertEquals(result, true);