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Perl substitute - the e modifier

Here's a graphic illustration of the use of the "e" for "execute" modifier used on the end of substitute operation in Perl.

The "s" for substitute allows you to replace a matched pattern with a STRING in which you can use special references like \1 or $1 for the first matched substring. If you want it to replace the matched pattern with the RESULT OF RUNNING CODE, you should add that extra e on the end.

In this example, the $emma variable ends up containing a corrupted email address which actually includes some code, whereas (with the "e"), the $emily variable results in a correct email address with the section before the "@" pushed to lower case.

$emma = 'Graham@wellho.net';
$emily = 'Graham@wellho.net';
 
$emma =~ s/(\w+)@/lc($1)."@"/;
$emily =~ s/(\w+)@/lc($1)."@"/e;
 
print ("$emma\n$emily\n");
 
__END__
 
Dorothy:plpw grahamellis$ perl swithe
lc(Graham)."@"wellho.net
graham@wellho.net
Dorothy:plpw grahamellis$

(written 2008-12-16)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
P212 - Perl - More on Character Strings
  [3927] First match or all matches? Perl Regular Expressions - (2012-11-19)
  [3707] Converting codons via Amino Acids to Proteins in Perl - (2012-04-25)
  [3650] Possessive Regular Expression Matching - Perl, Objective C and some other languages - (2012-03-12)
  [3630] Serialsing and unserialising data for storage and transfer in Perl - (2012-02-28)
  [3546] The difference between dot (a.k.a. full stop, period) and comma in Perl - (2011-12-09)
  [3411] Single and double quotes strings in Perl - what is the difference? - (2011-08-30)
  [3332] DNA to Amino Acid - a sample Perl script - (2011-06-24)
  [3322] How much has Perl (and other languages) changed? - (2011-06-10)
  [3100] Looking ahead and behind in Regular Expressions - double matching - (2010-12-23)
  [3059] Object Orientation in an hour and other Perl Lectures - (2010-11-18)
  [2993] Arrays v Lists - what is the difference, why use one or the other - (2010-10-10)
  [2877] Further more advanced Perl examples - (2010-07-19)
  [2874] Unpacking a Perl string into a list - (2010-07-16)
  [2834] Teaching examples in Perl - third and final part - (2010-06-27)
  [2801] Binary data handling with unpack in Perl - (2010-06-10)
  [2657] Want to do a big batch edit? Nothing beats Perl! - (2010-03-01)
  [2379] Making variables persistant, pretending a database is a variable and other Perl tricks - (2009-08-27)
  [2230] Running a piece of code is like drinking a pint of beer - (2009-06-11)
  [1735] Finding words and work boundaries (MySQL, Perl, PHP) - (2008-08-03)
  [1727] Equality and looks like tests - Perl - (2008-07-29)
  [1510] Handling Binary data (.gif file example) in Perl - (2008-01-17)
  [1336] Ignore case in Regular Expression - (2007-09-08)
  [1305] Regular expressions made easy - building from components - (2007-08-16)
  [1251] Substitute operator / modifiers in Perl - (2007-06-28)
  [1230] Commenting a Perl Regular Expression - (2007-06-12)
  [1222] Perl, the substitute operator s - (2007-06-08)
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [928] C++ and Perl - why did they do it THAT way? - (2006-11-16)
  [737] Coloured text in a terminal from Perl - (2006-05-29)
  [608] Don't expose your regular expressions - (2006-02-15)
  [597] Storing a regular expression in a perl variable - (2006-02-09)
  [586] Perl Regular Expressions - finding the position and length of the match - (2006-02-02)
  [583] Remember to process blank lines - (2006-01-31)
  [453] Commenting Perl regular expressions - (2005-09-30)

P669 - Perl - Data Munging
  [3764] Shell, Awk, Perl of Python? - (2012-06-14)
  [3335] Practical Extraction and Reporting - (2011-06-26)
  [2702] First and last match with Regular Expressions - (2010-04-02)
  [2129] Nothing beats Perl to solve a data manipulation requirement quickly - (2009-04-14)
  [1509] Extracting information from a file of records - (2008-01-16)
  [1316] Filtering and altering Perl lists with grep and map - (2007-08-23)


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