A macro system for Scheme by R. Kent Dybvig <email@example.com>. It is superior to the low-level system described in the Revised^4 Report (R4RS). Pattern variables are ordinary identifiers with essentially the same status as lexical variable names and macro keywords. The syntax is modified to recognise and handle references to pattern variables. Version 2.1 works with Chez Scheme and the Macintosh port runs under MacGambit 2.0
["Writing Hygienic Macros in Scheme with Syntax-Case", R. Kent Dybvig, IUCS TR #356, 6/92 (revised 7/3/92)].