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An Introduction to Perl Part I Jonathan Stanley CS265 An Introduction to Perl Part I Introduction Scalar Data Variables Operators If-Else Control Structures While Control Structures Standard Input Lists and Arrays Introduction What is Perl? Scalar Data Numbers Strings Perl has two types of numbers: A string is a sequence of characters Integers => 4 or 20 Floating point numbers => 2.3 or 4.5 In Perl, strings can have single or double quotes. Implementation => $var=4; or Implementation => $var=3.5; Implementation => $var=‘a’; Implementation => $var=“new/nLine”; Variables In Perl, variables are declared with the $ symbol. They may contain a combination of letters, numbers, and underscores but cannot begin with a number. Comments are also denoted as #. $Num2=5; #Num2 has the value of 5 $my_name=‘Jon’; #my_name has the value “Jon” Numerical Operators Assignment Operators =, +=, -=, *=, /=, %=, **= $var=265; $var-=265; $var+=265; Comparison Operators ==, !=, <, >, <=, >= $var==1; $var!=0; Arithmetic Operators +, -, *, /, %, ** $var=1+3; $var=9–4; $var=3*2; $var=8/2; $var=6%4; $var=3**2; String Operators Assignment Operators =, .= $var=“yes” $var.=“ or no” Comparison Operators eq, ne, lt, gt, le, ge $var eq “yes”; $var gt “apple”; Logical Operators &&, ||, ! ($var==“yes”) && ($var2==2) ($var==“yes”) || ($var2==2) ($var==“yes”) != ($var2==2) Contamination Operator . (dot symbol) “Jon”.“Stanley” Multiplier Operator x “yes”x3 If-Else Control Structures if ($class eq “CS265”) { print “What a good day :)” ; } else { print “What a bad day :(”; } While Control Structures while($counter <= 3) { $counter++; print $counter; } Standard Input $var=<STDIN> ; print “What is you name?"; chomp ($name = <>); print “What is your major?"; chomp ($major= <>); print “$name is currently studying $major at Drexel University."; Lists and Arrays A list is an ordered collection of scalars while an array is a variable that holds lists. @list1=(“jon”, “jacob”, “jingleheimer”, “schmidt”); @list2=(0..8); print @list1[1]; #prints jacob print @list2; #prints 0 1 2 … 8 push() - adds an element to the end of an array. unshift() - adds an element to the beginning of an array. pop() - removes the last element of an array. shift() - removes the first element of an array. @list1.shift(); @list1.unshift(); #After both, list1 contains 2 entries. @list2.push(9); #adds 9 to the end Questions?