I am trying to use a regex pattern with properties in an xsl:analyze
statement, like this:

B B B <xsl:analyze-string select="$stringtoproc" regex="\p{L}">

with the intention of capturing letters only. However, when using this
in an XSLT transformation in OxygenXML, I receive the following error:

Syntax error at char 2 in regular expression: Expected '{' after \112

The attribute value is treated as an attribute value template where an
expression in curly braces is evaluated as an XPath expression. So
either double the curly braces if
   regex="\p{{L}}"
or store the value in a variable and use it.

Because the regex attribute is an attribute value template, curly
brackets within the regular expression must be doubled. For example, to
match a sequence of one to five characters, write regex=".{{1,5}}". For
regular expressions containing many curly brackets it may be more
convenient to use a notation such as
regex="{'[0-9]{1,5}[a-z]{3}[0-9]{1,2}'}", or to use a variable.