Listing 2. Building sendmail from m4 Sources

# Ruleset 93 -- convert header names to masqueraded
# form
S93
# handle domain-specific masquerading
R$* < @ $=M . > $*      $: $1 < @ $2 . @ $M > $3
# Ruleset 94 -- convert envelope names to masqueraded
# form
S94
R$+                     $@ $>93 $1