Convert "xxxxxb#b" to "xxxxx<#>"

Where "xxxxx" can be any sub string and "#" can be any number. However "#" would rarely be more than two digits. The two "b" characters that are converted to "<" and ">" are always "b".

An example input string would be "abcdb9b" with the required return string being "abcd<9>".

I have a solution that appears work but it's ugly.

procedure( charReplace(string)
  let( ( inDex m1 m2 m3 mb str1 str2 )
    inDex = length(lindex(parseString(string "") "b" ?all t))
    m1 = pcreCompile( "b[0-9]+b$" )
    m2 = pcreCompile( "b$" )
    m3 = pcreCompile( "b[0-9]+>$" )
    mb = pcreCompile( "b" )
    if(pcreExecute(m1 string) then
      println("match m1")
      str1 = pcreReplace( m2 string ">" 0)
      if(pcreExecute(m3 str1) then
       println("match m3")
       str2 = pcreReplace( mb str1 "<" inDex - 1)
       println(str2)
      ) ; if
    ) ; if
  ) ; let
) ; proc

My main problem was how to replace the last 'b' with '>' and the second to last 'b' with '<'. I worked it out by first creating a new string with the last b (b$) replaced first and then operating on the new string to replace the second to last 'b'.

There must be a better way so I'm open to all comments, advice, suggestions, or questions.

Thanks in advance and cheers to all.