Perl References arrays and hashes can only contain scalars (numbers and strings)‏ if we want something more complicated (like an array of arrays) we use references references are scalars as well references are like pointers in C/C++

Creating References from existing variables: $scalar_ref = \$scalar_var; $array_ref = $hash_ref = \%hash_var;

Anonymous References anonymous arrays use []: $array_ref = [ 1, 2, [ “dog”, “cat”, “mouse” ] ]; anonymous hashes use {}: $hash_ref = { “height” => 175, “weight” => 67.8 }

Dereferencing scalar references: $$scalar_ref array references: $array_ref->[2] hash references: $hash_ref->{“height”}

Regular Expressions used to match patterns in strings most characters match themselves except for: \ | ( ) [ { ^ $ + ?. to match a special character, escape it with a \ e.g.: \\ \. \$

RE cont'd ^ matches the beginning of the string $ matches the end of the string. matches any character

RE quantifiiers * zero or more occurences + one ore more occurences ? zero or one occurences {n,m} between n and m occurrences {n,} at least n occurrences {n} exactly n occurrences

() in RE () used to group characers where more than a single character is to be quantified value matching pattern in () is stored for later use

Simple CGI Program #!/usr/bin/perl print "Content-type: text/plain\n\n"; print $ENV{"QUERY_STRING"};

Pattern Matching