Perl minimal matching

#!/usr/bin/perl -w

# practise how to use g flag and ? min match patten.

$string="<TR><TD>data1</TD><TD>data2</TD><TD>data3</TD></TR><TR><TD>data4</TD></TR>";

while ($string =~ /<TR>(.*?)<\/TR>/gi) {
        #$&: <TR><TD>data4</TD></TR>, patten in // all.
        #$1: <TD>data4</TD>, patten just in /()/, has order for example $1, $2......
        $match_1 = $1;
        while ($match_1 =~ /<TD>(.*?)<\/TD>/gi) {
                print $1 . " ";
        }
        print "\n";
}

#data1 data2 data3
#data4