.elseifdef (also #elseifdef) and .elseifndef (also #elseifndef)

.elseifdef macro

The same as .elseif except that it uses the .ifdef or .ifndef conditionals:

#define X marks_the_spot

#ifdef X
.echo "X is defined.\n"
#elseifdef Y
.echo "Y is defined.\n"
#else
.echo "Neither X nor Y are defined.\n"
#endif