Perl Hacks

Hack #7. Enforce Local Style

Keep your code clean without editing it by hand.

One of the first barriers to understanding code written by others is that their formatting style may not match yours. This is especially true if you find yourself maintaining code that, at best, has grown with little direction over the years. Whether you work with other developers and want to maintain a consistent set of coding guidelines, or you want to find some structure in a big ball of mud, perltidy can help untangle and bring consistency to even the scariest code.

The Hack

Install the CPAN module Perl::Tidy. This will also install the perltidy utility. Now you can use it!

From the command line

Run perltidy on a Perl program or module and it will write out a tidied version of that file with a .tdy suffix. For example, given poorly_written_script.pl, perltidy will, if possible, reformat the code and write the new version to poorly_written_script.pl.tdy. You can then run tests against the new code to verify that it performs just as did the previous version (even if it is much easier to read).

This command reformats the contents of some_ugly_code.pl so that it's no longer, well, ugly. How effective is it? The Perltidy docs offer an example. Before:

$_= <<'EOL'; $url = URI::URL->new( "http://www/" ); die if $url eq "xXx"; EOL LOOP:{print(" digits"),redo LOOP if/\\G\\d+\\b[,.;]?\\s*/gc;print(" lowercase"), redo LOOP if/\\G[a-z]+\\b[,.;]?\\s*/gc;print(" UPPERCASE"),redo LOOP if/\\G[A-Z]+\\b[,.;]?\\s*/gc;print(" ...