foreach my $loop_variable (@data_array) { 
    print $loop_variable;
}
[download]

or this:

foreach (@data_array) { 
    print $_;
}
[download]

As a side note, see how all your array elements are links? That is because you did not wrap your code in <code> tags. See Writeup Formatting Tips.

2) You are not declaring array elements so much as defining strings and storing those in your array. Your syntax will work so long as you have a comma separated list of strings. That means you can use pairs of single quotes, pairs of double quotes or any of a host of delimiters listed in Quote and Quote like Operators. For your case, you may be particularly interested in the qw() delimiter, since that uses whitespace to delimit your strings instead of commas.

"Do we need to declare array elemnts in double quotes"

@array1 = ('one','two','three');
@array2 = ("four","five","six");
print "@array1\n@array2";

#OUTPUT
one two three
four five six
[download]

@array = qw(one two three);
print @array, "\n";
print "@array\n";
print '@array\n';
__END__
onetwothree            #array elements are fused.
one two three          #spaced and the "\n" replaced with a new line.
@array\n               #prints @array and "\n" as literals.
[download]

use strict;    #a good habit to start your program with line
use warnings;  #another good habit too...

my @array1 = ("one", "two", "five");
my @array2 = ("three","four");

my @array3 = ("one","two",@array2,"five");
my @array4 = ("one","two",'@array2',"five");
my @array5 = ("one","two","@array2","five");
print "@array3\n";
print "@array4\n";
print "@array5\n";
[download]

You can loop through your array with a for loop iteration too and using an incremented index allows you to access array elements in turns.

@array = qw(one two three four);
for($index=0;$index<=$#array;$index++){
     print $array[$index],"\n";
     }
[download]

Update: Added examples...

@array = qw(one two three);
print @array, "\n";
print "@array\n";
print '@array\n';
__END__
onetwothree            #array elements are fused.
one two three          #spaced and the "\n" replaced with a new line. 
@array\n               #prints @array and "\n" as literals.
[download]



I understand first output as all the array elements are printed in a row.

I dont understand second output. When print command is used with array name in quotes, output has a space between elements. where does this space come from ?

In the third output, everything in single quotes is printed as literal. Does it mean that anything in single quotes is treated as literal and will be printed as is. Anything in double quotes will be treated as string value with variables getting its values from the code ?

I dont understand second output. When print command is used with array name in quotes, output has a space between elements. where does this space come from ?

The Perl print built-in prints a list with the $, special variable interpolated between each item.

Double-quoted strings (which have nothing directly to do with print) interpolate arrays with the $" special variable interpolated between each array element. See the documentation in perlvar for the default values of the  $, and  $" special variables.

In the third output, everything in single quotes is printed as literal. Does it mean that anything in single quotes is treated as literal and will be printed as is.

Yes. Whether printed or not, there is no interpolation in single-quoted strings. The  \ (backslash) character has limited effect as an escape under conditions explained in the docs on single-quoted strings linked by other respondents.

Anything in double quotes will be treated as string value with variables getting its values from the code ?

Yes and no. Double-quoted strings interpolate scalar and array variables as per the docs.

>perl -wMstrict -le
"my @array = ('one', qw(two three), qq{four});
 print @array;
 $, = 'FOO';
 print @array;
 print qq{@array};
 $\" = 'BAR';
 print qq{@array};
"
onetwothreefour
oneFOOtwoFOOthreeFOOfour
one two three four
oneBARtwoBARthreeBARfour
[download]

is anything within single quotes is always treated as literal in print statement ?
anything in double quotes is treated as string with variables getting their values from the code ?
whats the difference between when an array elements are declared in single quotes, double quotes and without quotes ? I tried out all the ways and I get the same result.

if I want to loop through this array using foreach, do I need to use  $data_array variabke only or can I use any variable ?

foreach $loopvariable (@data_array)
{ print $loopvariabe ; }
[download]

does it mean that  $loopvariable will be assigned the elelments of @data_array one by one ?

foreach (@data_array)
{ print $data_array ; } #this looks like wrong syntax
[download]

Do we need to declare array elemnts in double quotes only or can we declare it in single quotes also ? what if array elements are declared without any quotes ? will it be a syntax error ?

Not to discourage asking questions, but even without Resort to The Fine Manuals linked by other respondents, these questions can also be answered by experimentation. Note: Using warnings and strictures (use warnings; use strict; or  -wMstrict on the command line) while experimenting can be very informative.

>perl -wMstrict -le
"my @array = qw(one two three);
 for my $loopvariable (@array) {
   print $loopvariable;
   }
"
one
two
three

>perl -wMstrict -le
"my @array = qw(one two three);
 for (@array) {
   print $array;
   }
"
Global symbol "$array" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.
[download]

Note also that the loop variable is aliased to the elements of the list over which the loop iterates; it can be used to change them (if they are changeable!).

>perl -wMstrict -le
"my @array = ('two', 'three', 'four');
 for my $loopvariable (@array) {
   ++$loopvariable;
   }
 print qq{@array};
"
twp thref fous
[download]