05 Aug 2020 11:37:50 UTC
- Distribution: Filter
- Module version: 1.60
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- License: perl_5
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Filter::m4 - M4 source filter
use Filter::m4; use Filter::m4 'prefix';
This source filter pipes the current source file through the M4 macro processor (
m4) if it is available.
As with all source filters its scope is limited to the current source file only. Every file you want to be processed by the filter must have the following line near the top.
Here is a small example that shows how to define and use an M4 macro:
use Filter::m4; define(`foo', `$1 =~ s/bar/baz/r') $a = "foobar"; print "a = " . foo(`$a') . "\n";
The output of the above example:
a = foobaz
By default, M4 uses ` and ' as quotes; however, this is configurable using M4's
$2, etc., to indicate arguments in macros. To avoid clashes with Perl regex syntax it is recommended to use Perl's alternative forms
The following keywords in M4 and Perl are identical:
eval format index mkstemp shift substr
If you need such keywords in your Perl code you have to use one of the following three solutions.
Protect the keyword with M4 quotes, for example
Redefine the problematic M4 builtin using
defn, as outlined in section Renaming macros of the M4 info manual.
prefixoption. This adds the prefix
m4_to all M4 builtins (but not to user-defined macros). For example, you will have to use
17th March 2018.