my $v = { R3R3_1_IF=>"xx", R3R3_2_IF=>"yy", R3R3_3_IF=>"zz" };
my $pic = 1;
my $key_MS = sub { "R3R3_${pic}_IF"; };
print "set service-interface $v->{&$key_MS}.0\n";
$pic++;
print "set service-interface " . $v->{&$key_MS} . ".0\n";
$pic++;
print "set service-interface ", $v->{&$key_MS}, ".0\n";

__END__

set service-interface xx.0
set service-interface yy.0
set service-interface zz.0