The Unicode Character Database groups code points into a number of blocks such as Basic Latin (ASCII) and so on. The set containing all characters that have block name X (with all white space stripped) can be identified with a block escape \p{IsX}. The complement of this set is specified with the block escape \P{IsX}.
For more information, see the Appendix F Regular Expressions in the W3C XML Schema Datatypes specification (http://www.w3.org/TR/xmlschema-2).
IsBlock ::= 'Is' [a-zA-Z0-9#x2D]+
The following example shows a block escape to identify the ASCII character for Basic Latin.
\p{IsBasicLatin}
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