1. Introduction to Perl
Jarrad Battaglia

2. What I will be covering
Foreach statements
Hashes
Splits

3. Hashes
Hashes are very similar to arrays, but use strings instead of numbers for indexing
Hashes use a key,value system
Hash indices are called keys
Say you create an array A(1..10)
Hash(“one”,”1”,”two”,”2”)
Hash{“one”} = “1”
While Array [0] = 1

4. Reverse Hash Add new hash element Add multiple values to hash
Format: $hash{“key”} = “value”;
$hash{“one”} = “1”;
Add multiple values to hash
Format: %hash(“key1”, “value1”,”key2”, “value2”);
%hash($key1 => $value1, $key2 => $value2)
Reverse hash – so keys become values and values become keys
%reverse_hash = reverse %hash;

5. Additional Hash Commands
Delete one key-value from hash list
delete $hash{key};
Delete all keys and values
%hash = ();
Check if key exists
If(exists $hash{key});
Use variables in hash
$hash{$key} = $value;

6. Hash to Array Hash to array Array to Hash %hash (“one”,”1”,”two”,”2”);
@list = %hash
List now has a size of 4
Array to Hash
%hash = ();
%hash
Hash is now back to regular

7. Foreach statement Are used to iterate every value of an array or hash
In an array the foreach statement will loop through every value of a list
In a hash it will loop through the key, then go to its value, unless specified

8. Foreach examples Loop through hash with foreach Loop through a list
foreach $hash (keys %hash) { print “keys\n”}
Loop through a list
foreach $list {print “$list\n” }
foreach { print “$_\n” }
Loop through numbers
foreach (1..10) {print “$_\n”}

9. Foreach Example

10. Split Function
The split function will split a scalar string into an array of strings
For example
@stringlist = split(/ /,"string into spaces");
foreach { print “$_\n”;
This would print “string”, “into”, “spaces” all on different lines

11. Split Examples Split two sentence into two Split input by spaces
$string = “This is one. This is two”
%splitstr = split(/\./,$string);
Foreach(splitstr){print “$_\n”;}
Split input by spaces
$input = <STDIN>;
foreach (split(“ “, $input)) { print “$_\n”;}

12. Hash Example