my @data1 = ( "a 1 a", "a 2 T", "a 3 C" );
my @data2 = ( "a 2 Y", "a 3 R", "a 4 Q", "b 5 R" );

for ( @data2 ) {
    my ($match) = $_ =~ /^(\w\s+\d)/;
    if ( grep { /$match/ } @data1 ) {
            print  "$_\n";
    }
}

##</code><code>##

$ perl compare.pl
a 2 Y
a 3 R

##</code><code>##

my @results;
for my $elem ( @data1 ) {
    my ($match) = $elem =~ /(\w\s+\d)/;
    @results = grep { /$match/ } @data2;
}
 print "$_\n" for @results;

##</code><code>##

$ perl compare.pl
a 3 R