s/^
    \s*
    my \s*
    \(?\s*
      \$page # page is the variable
    \s*\)?
    \s*
      =
    \s*
    \&? # function may or may not be explicitly contexted
    create_page # function name
    \s*
    \(\s* # Begin param

      ([^,]+?), # 1st param
      \s*
      ([^,]+?), # 2nd param
      \s*
      ([^,]+?), # 3th param
      \s*
      ([^,]+?) # 4th param

    \s*\) # End param
    ;
  /your_replace_string/x;