my @link;

while (<DATA>) {
    my @l = m~<a\s[^>]+>([^<>]+)</a>~ig;
    next unless 3 == @l;
    push @link, grep {$_ =~ /^[RT]\d+$/} @l;
}

print "$_\n" for @link;

_ _ D A T A _ _
<A HREF="/pub/databases/transfac/doc/gene1.html#BS" target="_new">BS</A>     -202   -135   <A HREF="/cgi-bin/pub/databases/transfac/getTF.cgi?AC=R00929">R00929</A>; HS$IFNB_14.
<A HREF="/pub/databases/transfac/doc/gene1.html#BS" target="_new">BS</A>     -167    -94   <A HREF="/cgi-bin/pub/databases/transfac/getTF.cgi?AC=R00916">R00916</A>; HS$IFNB_01; Binding factors: R2 <A HREF="/cgi-bin/pub/databases/transfac/getTF.cgi?AC=T00712">T00712</A>.
<A HREF="/pub/databases/transfac/doc/gene1.html#BS" target="_new">BS</A>     -100    -61   <A HREF="/cgi-bin/pub/databases/transfac/getTF.cgi?AC=R00917">R00917</A>; HS$IFNB_02; Binding factors: IRF1 <A HREF="/cgi-bin/pub/databases/transfac/getTF.cgi?AC=T00422">T00422</A>, IRF-2
<A HREF="/pub/databases/transfac/doc/gene1.html#BS" target="_new">BS</A>     <A HREF="/cgi-bin/pub/databases/transfac/getTF.cgi?AC=T00425">T00425</A>.