Not totally sure what you are after, but your code doesn't compare and isn't well laid out - see perlcritic and perlstyle. As a beginner (or anyone else) you should always use warnings and strict. You may also find diagnostics helpful - it will give you fuller explanations of warnings and their possible origin.

Making a few guesses as to what you wanted (two identical elements per line?) I came up with the following:

use warnings;
use strict;

use Data::Dumper qw/Dumper/; # very useful for debugging
++$|;
my @array = (<DATA>);

# check input
print "INPUT :\n" . Dumper \@array;

foreach my $line (@array){
    chomp $line; # remove trailing newline
        # ignore empty lines
    next unless (defined$line && $line ne '');   
        # split on space      
    my @t = split /\s+/, $line;
        # accept lines with two, identical elements
    if ( scalar @t == 2 && $t[0] eq $t[1] ){
        print "MATCH : $line\n";
    }
    else {
        print "NO : $line\n";
    }
}
# gives -
#INPUT :
#$VAR1 = [
#          'file
#',
#          '
#',
#          'ass ass
#',
#          '
#',
#          'array
#',
#          '
#',
#          'rat rasa
#',
#          '
#',
#          'arrow ant
#',
#          '
#',
#          'sad'
#        ];
#NO : file
#MATCH : ass ass
#NO : array
#NO : rat rasa
#NO : arrow ant
#NO : sad
__DATA__
file

ass ass

array

rat rasa

arrow ant

sad
[download]

There are shorter ways to do this using lookaheads and regular expressions but it is usually best to stick with something clear! HTH.