You are Suffering From Buffering. In short, adding the following line after your use statements will remove the problem:

$|++;
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use strict;
use warnings;
$|++ ;
my $text="this is a sample";
my @word=split(//, "$text");
for (@word){
        print "$_";
        sleep 2;
}
print "\n";
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Hi there, the answer to your question is the buffering issue but here are a coulpe more points that may be of interest.

#!/usr/bin/perl -w  
# -w is the old way to do use warnings, you can drop it
# as you use warnings anyway

use strict;
use warnings;

my $text="this is a sample";
# no need to make the following intermediate array
# no need to use the brackets for split unless to disambiguate
# no need to "quote" $text
my @word=split(//, "$text");
# if we loose @word we can just loop directly on the split
for (0 .. $#word){
        # no need to quote $word[$_] here either
        print "$word[$_]";
        sleep 2;
}
print "\n";

######################
# new shorter code.. #
######################

#!/usr/bin/perl
use strict;
use warnings;
$|++;

my $text="this is a sample";

for (split //, $text) {
        print;   # defaults to print $_, some don't like this style
        sleep 2;
}
print "\n";
[download]

Cheers,
R.

Someone has just asked a very similar question: Sleep Not Sleeping when using without "\n".