/MULTI command[;command[...]]

Runs specified mcabber commands one by one. Note, that it will not honour any backslash-escapes, parentheses, quotes etc - it will just split line on semicolons.
Example:
 /set hook-post-connect = multi group fold Transports; group fold Old
 /multi if fifo_name; then load fifo; else echo "fifo_name not set, fifo module not loaded"