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For 2023 - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Finding all matches to a pattern in Perl regular expressions

A regular expression usually matches the leftmost occurrence of a pattern within an incoming (source) string.

This doesn't matter if all you're looking to do is find whether or not your source string contains something ... but if you're looking to make use of the part that matched, then it does make a difference. Consider
  $us = 'I am graham@wellho.net and you are pinkpanther@frenchdetectives.fr';
and the match

This will match graham@wellho.net every time you run it in Perl, and never pinkpanther@frenchdetectives.fr .

What if you want to match that second email address, then? You can add a modifier after the end of the regular expression - the single letter g which stands for "global".

* In a scalar content, but used in a loop, a global match carries on where the last match left off on each successive time around the loop, thus letting you loop though all valid, non-overlapping matches in the string. And when there are no more, a false result will be returned. Thus:

  while ($us =~ /\S+\@\S+/g) {
    print "Emma is $&\n";

Will return each match it turn. By contrast, without the g this program would give you an infinite loop.

There are, as always, multiple ways of doing the same thing in Perl. If you use the g modifier in a list context (for example return the result of the match into a list), that list will be assigned to all non-overlapping matches. Thus:

  @gotted = $us =~ /\S+\@\S+/g;
  print "We got @gotted\n";

will output

  We got graham@wellho.net pinkpanther@frenchdetectives.fr

Complete program [here]. As taught during our Learning to program in Perl / Perl Programming training classes.

(written 2011-12-09, updated 2011-12-17)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
G206 - Well House Consultants - Our training centre
  [53] Drive the drive - (2004-09-18)
  [256] Spring is in the air - (2005-03-24)
  [448] Out of the norm. - (2005-09-23)
  [627] JIT or JAU - (2006-02-27)
  [640] Training Centre Pictures - (2006-03-09)
  [1200] Training information - England, Scotland, Wales and Ireland - (2007-05-22)
  [1240] Fancy going to Glastonbury? - (2007-06-22)
  [2126] Weeding out old phone numbers - (2009-04-11)
  [2537] Faster network, but not faster browsing until ... - (2009-12-14)
  [2538] Open Source Training Centre and Courses for 2010 - (2009-12-16)
  [2660] One number for Well House - 01225 708225 - (2010-03-04)
  [2926] Journey times to Melksham, Wiltshire - (2010-08-17)
  [2943] Our facilities to support Well House Consultants Courses - (2010-09-02)
  [4012] A course is not just for a year - its for a career - (2013-02-20)

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Some other Articles
Well House Manor - perhaps the best hotel rooms in Melksham
Dark mornings, dog update, and Python and Lua courses before Christmas
Using Perl to generate multiple reports from a HUGE file, efficiently
The difference between dot (a.k.a. full stop, period) and comma in Perl
Finding all matches to a pattern in Perl regular expressions
Looking for hotel rooms in Melksham over Christmas? We still have some availability
Some different pictures from Melksham
What order are operations performed in, in a Perl expression?
I loves Melksham
Easy session example in PHP - keeping each customers data apart
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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