Hi MynameisAchint,
To really get the help you want it will be wonderful if you follow the advice giving in How do I post a question effectively?.

...I wish to run a for loop for that array...
Instead of using a for loop as used in C, why not use for/foreach as Perl like thus:

  my @array_data = qw( 21 45 perl 28 monks);

   foreach my $data (@array_data){
     print $data,"\n";
   }
[download]

Update:
However, if you want to iterate over the array, using the index of the array, Perl also does that for you very cleanly.

 my @array_data = (21,45,'perl',28,'monks',' ','togo');

   for my $num (0..$#array_data){
     print $num,': ',$array_data[$num],"\n";
   }
[download]

0: 21
1: 45
2: perl
3: 28
4: monks
5:  
6: togo
[download]

Please, note that I used foreach and for inter-changeably.
And please don't forget that array index start from 0 and not 1, as used in your OP for loop.
Hope this helps