Finding a Substring with index

Finding a substring depends on where you have lost it. If you happen to have lost it within a bigger string, you’re in luck because the index function can help you out. Here’s how it … Read the rest

Moving Around the Directory Tree

Your program runs with a “working directory,” which is the starting point for relative pathnames. That is, if you refer to the file fred, that means fred in the current working directory.

The chdir … Read the rest

File Test Operators

Before we start a program that creates a new file, let’s make sure that the file doesn’t already exist so that we don’t accidentally overwrite a vital spreadsheet datafile or that important birthday calendar. For this, we … Read the rest

There is a lot more to Perl than what we’re able to show you in this book, and there are a lot of people doing a lot of interesting things with Perl. If there is a problem to solve, then … Read the rest

The unless Control Structure

In an if control structure, the block of code is executed only when the conditional expression is true. If you want to execute a block of code only when the conditional is false, change … Read the rest

Substitutions with s///

If you think of the m// pattern match as being like your word processor’s “search” feature, the “search and replace” feature would be Perl’s s/// substitution operator. This simply replaces whatever part of a variable matches a … Read the rest

Matches with m//

We’ve been writing patterns in pairs of forward slashes, like /fred/. But this is actually a shortcut for the m// (pattern match) operator. As you saw with the qw// operator, you may choose any pair of … Read the rest

Using Simple Patterns

To match a pattern (regular expression) against the contents of $_, simply put the pattern between a pair of forward slashes (/), like we do here:

$_ = "yabba dabba doo"; 
if (/abba/) { 
    print "It 

Hash Element Access

To access an element of a hash, use syntax that looks like this:
$hash{$some_key}
This is similar to what we used for array access, but here we use curly braces instead of square brackets around the subscript(key). … Read the rest