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]