Numbers
All numbers are stored as doubles...no integer division problems
You can split up long numbers with _ (Example: 1234 could be 12_34)
Numeric Operators
+, -, *, /, % (mod), ** (power)
Strings
Single quoted - 'literal' strings
'a\nb' really is:
a,\,n,b
Double quoted - interpolated
"a\nb" is:
a
b
Control chars on p.24
String Operators
. - concatenation
print "a" . "b"; #prints ab
x - repetition
print "a" x 5; #prints aaaaa
Scalar Variables
Holds a single scalar value
Starts with a $, cannot have a number first, but then an alphanumeric
char or _
Legal Examples: $a $Alan1 $Joe_Blow
Illegal Examples: y6 $1a $r%4 (Avoid $_...Perl uses this)
Same variable can hold string or numeric data if reassigned:
$a=3;
$a="hello"; #This is ok
Binary Assignment Operators
+=, -=, *=, /=, **=, .=
$a=1; #$a=1
$a+=4; #$a=5
$a-=3; #$a=2
$a*=3; #$a=6
$a/=2; #$a=3
$a**=2; #$a=9
$a.='a'; #$a=9a
Print Operator
Simple way to perform output
Examples:
print "Hello"; #prints Hello
$a=3;
print $a; #prints 3
print '$a'; #prints $a
print "$a"; #prints 3
Operator Precedence
p. 32 (Basically just know: 1. () 2. *,/ 3. +.-)
Comparison Operators
Comparison Numeric String Equal == eq Not Equal != ne Less Than < lt Greater Than > gt Less than or equal to <= le Greater than or equal to >= ge Note: "0" lt "9" lt "A" lt "a"
Basically, if comparing strings, use one from the string col, if comparing values, use one from the numeric col
if, if...else
if (boolean) {
} else {
}
A boolean is a true or false value, eg: 1<2 is true, "3" eq "2" is false, etc
Input From The Keyboard
$input = <STDIN>;
Chomp/Chop
chomp($input) - Deletes \n from end of $input
chop($input) - Deletes last char from $input
While
while (boolean)
{
}
Undef/Defined
New variables are undef
Check a variable with defined($input)
The value undef is considered to be false