how to avoid leading white spaces

[rusi]

The efficiently argument is specious. [This is a python list not a C
or assembly list]

The real issue is that complex regexes are hard to get right -- even
if one is experienced.
This is analogous to the fact that knotty programs can be hard to get
right even for experienced programmers.

The analogy stems from the fact that both programs in general and
regexes in particular are a code.
Regex in particular is a code for an interesting class of languages --
the so-called regular languages.  And like all involved cod(ing), can
be helped by a debugger.

And just as it is a clincher for effective C programming to have a C
debugger whereas it is less so for python, the effective use of
regexes needs good debugger(s).

I sometimes use regex-tool but there are better I guess (see
http://bc.tech.coop/blog/071103.html )
Most recently there was mention of a python specific tool: kodos
http://kodos.sourceforge.net/about.html

In short I would reword rurpy's complaint to: Regexes should be
recommended along with (the idea of) regex tools.