Scalar Variable in Perl
What are the Scalar Variables?
How to do string Concatenation and Variable Substitution?
Explanation
Scalar Variable is a simple data that can be manipulated very easily by Perl. Numbers and Strings are basic scalar variables.
In Perl, integers can be expressed in decimal (base 10), hexadecimal (base 16) or octal (base 8) notation. Octal numbers are preceded by a 0 (zero).Perl internally considers integer as a double precision floating point value. Integer cannot be delimited by comma instead Perl allows underscore to seperate inetegers.
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
#floating-point values
$x = 4.15;
$y = -7.78;
#integer values
$a = 4000;
$b = -20;
print "$xn";
print $a; Result :
4.15 4000
The number can also accept a string ie., $a=20 is similar to $a="20".
The string defines a sequence of characters which can be defined in a single or double quotes.But when using Double quotes one has to carefully use the escape character "\" to get the correct display.
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
print "Sam says, "Give me $200"."; Result :
Server Error!
In the above example "$" is used for variable substitution and also as a symbol.Perl will assume that the string ends at the second double quotes. To get the correct display the string has to be escaped as below.
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
print "Sam says, \"Give me $200\"."; Result :
Sam says, "Give me $200"
If single quotes is used no need to escape a string as below.
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
print 'Sam says, "Give me $200".'; Result :
Sam says, "Give me $200".
In perl strings can be concatenated using the concatenation operator ".", but if the string contains quotes, carriage returns, backslashes, all these special characters need to be escaped with a backslash.
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
$a = "Hiox, India's";
$c = "Hosting Company";
$concat = $a ." leading Web". $c;
print $concat; Result :
Hiox, India's leading WebHosting Company
In the above example the strings "$a", "$b","$c" is concatenated using the "." operator.
Variable substitution means that variables within a double-quoted string will be substituted by their values at the time the statement is evaluated.This is not allowed when using a single quote, but when double quotes is used variable substitution is accepted.
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
$cel=40;
$fah = ($cel * 1.8) + 32;
print "The $cel degrees Celsius is $fah fahrenheit n";
print 'The $cel degrees Celsius is $fah fahrenheit '; Result :
The 40 degrees Celsius is 104 fahrenheit
The $cel degrees Celsius is $fah fahrenheit
In the above example first the value of the variables "$cel","$fah" are substituted as its given between double quotes. In the second print statement the string is given within single quotes so "$cel","$fah" is printed as it is.
Number:
In Perl, integers can be expressed in decimal (base 10), hexadecimal (base 16) or octal (base 8) notation. Octal numbers are preceded by a 0 (zero).Perl internally considers integer as a double precision floating point value. Integer cannot be delimited by comma instead Perl allows underscore to seperate inetegers.
Example :
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
#floating-point values
$x = 4.15;
$y = -7.78;
#integer values
$a = 4000;
$b = -20;
print "$xn";
print $a;
4.15 4000
The number can also accept a string ie., $a=20 is similar to $a="20".
String:
The string defines a sequence of characters which can be defined in a single or double quotes.But when using Double quotes one has to carefully use the escape character "\" to get the correct display.
Example :
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
print "Sam says, "Give me $200".";
Server Error!
In the above example "$" is used for variable substitution and also as a symbol.Perl will assume that the string ends at the second double quotes. To get the correct display the string has to be escaped as below.
Example :
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
print "Sam says, \"Give me $200\".";
Sam says, "Give me $200"
If single quotes is used no need to escape a string as below.
Example :
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
print 'Sam says, "Give me $200".';
Sam says, "Give me $200".
String Concatenation:
In perl strings can be concatenated using the concatenation operator ".", but if the string contains quotes, carriage returns, backslashes, all these special characters need to be escaped with a backslash.
Example :
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
$a = "Hiox, India's";
$c = "Hosting Company";
$concat = $a ." leading Web". $c;
print $concat;
Hiox, India's leading WebHosting Company
In the above example the strings "$a", "$b","$c" is concatenated using the "." operator.
Variable Substitution:
Variable substitution means that variables within a double-quoted string will be substituted by their values at the time the statement is evaluated.This is not allowed when using a single quote, but when double quotes is used variable substitution is accepted.
Example :
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
$cel=40;
$fah = ($cel * 1.8) + 32;
print "The $cel degrees Celsius is $fah fahrenheit n";
print 'The $cel degrees Celsius is $fah fahrenheit ';
The 40 degrees Celsius is 104 fahrenheit
The $cel degrees Celsius is $fah fahrenheit
In the above example first the value of the variables "$cel","$fah" are substituted as its given between double quotes. In the second print statement the string is given within single quotes so "$cel","$fah" is printed as it is.
