"Perl for Perl Newbies" - Part 2Regular Expressions".", "[ ... ]"

7.2. ".", "[ ... ]"

In this slide we will learn how to specify any character or that a character will be one of a range of several possible characters.

The "." stands for any character

By putting a .character inside a regular expression, it means that it can match any character, excluding a newline. For example, the following snippet matches 5 letter words that start with 'l' and end with 'x':

use strict;
use warnings;

my
$string =
lc(
shift(
@ARGV));

if (
$string =~
/
l
...
x
/)
{

print
"True
\n
";
}
else
{

print
"False
\n
";
}

The [ ... ] specifies more than one option for a character

When square brackets appear, one can specify more than one character inside them as option for matching. If the first character is ^then they will match everything that is notone of the characters.

One can specify a range of characters with the hyphen. For example the pattern [a-zA-Z0-9_]matches every alpha-numeric character.

Here's an example that checks if a valid identifier for a perl variable is present in the string:

use strict;
use warnings;

my
$string =
lc(
shift(
@ARGV));

if (
$string =~
/
\$[A-Za-z_]
/)
{

print
"True
\n
";
}
else
{

print
"False
\n
";
}

Written by Shlomi Fish