An Introduction to Perl Part I Emily Goldberg

An Introduction to Perl – Part I Emily Goldberg

Scalar Data �Scalar – holds one piece of data • Numbers: Floating-Point Integer Non-decimal 3. 11023 -12 0377 octal -2. 7 e 32 3_814_524_705 0 xff hex 0 b 1111 binary

Scalar Data (cont’d. ) • Strings: Single-Quoted 'hellonthere' Double-Quoted hellonthere “hellonthere” hello there $string="world"; print "hi $string n!"; hi world !

Variables �Use $ prefix to denote a variable • Ex. - $_points=5; $name 2=‘Larry’; Variable names can contain letters, numbers, and underscores, but may NOT begin with a number.

Operators �Number Operators Operation Operator Add + Subtract - Multiply * Divide / Modulus % 10. 5%3. 2 = 1 Exponentiation ** 2**3 = 8 Assign =, *=. += Comparison ==, !=, <, >, <=, >= Example

Operators (cont’d. ) �String Operators Operation Operator Example Concatenation . "hello". "world" helloworld Repetition x “hello”x 3 hellohello Comparison eq, ne, lt, gt, le, ge Assignment =, *=. +=, . = $name 2. =‘ Lee’ larry Lee

Automatic Conversion Operations Results "hello“. 3 * 5 “hello 15" “ 12” * “ 3” 36 "12 fred 34" * " 12 - ”fred” 3" 36 12

Standard Input/Output �Output • Ex. - print "The answer is ", 6 * 7, ". n"; �Input • Ex. - $line=<STDIN>; • Remove “n”- chomp($line);

Control Structures: if-else �if ($language eq “Perl”) { print “Always use curly braces!” ; } else { print “ Who knows? !”; }

Control Structures: while �while(defined($line=<STDIN>)) {chomp($line); print “This line was: $line n”; } �while(<>) { chomp; print “This line was: $_ n”; }

Lists and Arrays �A list is an ordered collection of scalars. �An array is a variable that contains a list. A list with five elements

Lists and Arrays(cont’d. ) �@numbers=(1, 2, 3, 4); �@numbers=(1. . 4); �numbers[0]=‘one’; �print $numbers[$#numbers]; �$a=pop( @numbers); �push( @numbers, $a+3);

Questions?

Refrences �Learning Perl by Randal Schwartz and Tom Phoenix (Via Drexel Library electronic resources) �“Perl Basics” (http: //www. cs. drexel. edu/~knowak/cs 265_ fall_2009/perl_basics. pdf)