p4, the Perl based macro processor.  v0.2

When cpp and m4 are insufficient, there is p4.
New, with the power of Perl. *ting*

p4 has two macro prefix characters $ and &. You can
escape these characters with a backslash \ to prevent
macro expansion (e.g. \$ and \&). The \ character will
be removed in the output. Generally speaking, $ is used
for getting values, & is used to eval code. \&() returns
a value, where as \&{} does not.

There is currently only one builtin macro \&include().
&include("hello.p4")

\$who=$who

You can define new macro functions.
&{
  sub who {
    return $_[0] || $who;
  }
}

\&who=&who
\&who("me")=&who("me")

Hello &who

&{$foo = 'bar'}
Example of how multiple \ characters are handled for $ and &.
\$foo=$foo
\\$foo=$foo
\\\$foo=$foo

You can enclose macros in braces.

\${foo}z=${foo}z

\&(\$foo)=&($foo)

\&(length(\$foo))=&(length($foo))

You can address arrays and hashes.
&{@var = ('a','b','c')}
\$var[0]=$var[0]
\${var[0]}=${var[0]}
\&(\$var[0])=&($var[0])

&{
  $map{'one'} = 1;
  $map{'two'} = 2;
  $map{'2'} = 'two';
  $map{'three'} = 3;
}
\$map{'one'}=$map{'one'}
\${map{'two'}}=${map{'two'}}
\${map{\$map{'two'}}}=${map{$map{'two'}}}
\${map{\$map{'2'}}}=${map{$map{'2'}}}
\&(\$map{'three'})=&($map{'three'})


Usage: p4 file.p4 [file2.p4 ...] >output