+$ known_extensions = ""
+$ xxx = ""
+$ OPEN/READ CONFIG 'manifestfound'
+$ext_loop:
+$ READ/END_OF_FILE=end_ext/ERROR=end_ext CONFIG line
+$ IF F$EXTRACT(0,4,line) .NES. "ext/" .AND. -
+ F$EXTRACT(0,8,line) .NES. "vms/ext/" THEN goto ext_loop
+$ line = F$EDIT(line,"COMPRESS")
+$ line = F$ELEMENT(0," ",line)
+$ line_len = F$LENGTH(line)
+$ IF F$EXTRACT(line_len - 12,12,line) .NES. "/Makefile.PL" THEN goto ext_loop
+$ IF F$EXTRACT(0,4,line) .EQS. "ext/" THEN -
+ xxx = F$EXTRACT(4,line_len - 16,line)
+$ IF xxx .EQS. "DynaLoader" THEN goto ext_loop ! omit
+$ IF xxx .EQS. "SDBM_File/sdbm" THEN goto ext_loop ! sub extension - omit
+$ IF F$EXTRACT(0,8,line) .EQS. "vms/ext/" THEN -
+ xxx = "VMS/" + F$EXTRACT(8,line_len - 20,line)
+$ known_extensions = known_extensions + " ''xxx'"
+$ goto ext_loop
+$end_ext:
+$ close CONFIG
+$ DELETE/SYMBOL xxx
+$ known_extensions = F$EDIT(known_extensions,"TRIM,COMPRESS")
+$ dflt = known_extensions
+$ IF ccname .NES. "DEC" .AND. ccname .NES. "CXX"
+$ THEN
+$ dflt = dflt - "POSIX" ! not with VAX C or GCC
+$ ENDIF
+$ dflt = dflt - "ByteLoader" ! needs to be ported
+$ dflt = dflt - "DB_File" ! needs to be ported
+$ dflt = dflt - "GDBM_File" ! needs porting/special library
+$ dflt = dflt - "IPC/SysV" ! needs to be ported
+$ dflt = dflt - "NDBM_File" ! needs porting/special library
+$ dflt = dflt - "ODBM_File" ! needs porting/special library
+$ dflt = dflt - "Sys/Syslog" ! needs porting/special library "GDBM_File macro LOG_DEBUG"
+$ IF .NOT. Has_socketshr .AND. .NOT. Has_Dec_C_Sockets
+$ THEN
+$ dflt = dflt - "Socket" ! optional on VMS
+$ ENDIF
+$ dflt = F$EDIT(dflt,"TRIM,COMPRESS")
+$!