Regular expressions

Regular expressions
You are encouraged to solve this task according to the task description, using any language you may know.

The goal of this task is

• to match a string against a regular expression
• to substitute part of a string using a regular expression

Perl

Interpreter: perl, v5.8.8

Test

$string = "I am a string";
if ($string =~ /string$/) {
  print "Ends with 'string'\n";
}

if ($string !~ /^You/) {
  print "Does not start with 'You'\n";
}

Substitute

$string = "I am a string";
$string =~ s/ a / another /; # makes "I am a string" into "I am another string"
print $string;

Test and Substitute

$string = "I am a string";
if ($string =~ s/\bam\b/was/) { # \b is a word border
  print "I was able to find and replace 'am' with 'was'\n";
}

Options

# add the following just after the / for additional control
# g = globaly (match as many as possible)
# i = case-insensitive
# s = treat all of $string as a single line (incase you have line breaks in the content)
# m = multi-line (the expression is run on each line individually)
 
$string =~ s/i/u/ig; # would change "I am a string" into "u am a strung"