掉的<font>内容,但保留<br>
$_="gggg<FONT color=red>uijfae<BR>jifjea<BR>jfie</FONT>sadfeasfef<FONT color=red>uijfae<BR>jifjea<BR></FONT>sadfe";
$i=0;
s|(?{$i = 0})<FONT color=red>.*?(<BR>(?{$i++}))*?</FONT>|"<BR>" x $i|ge;
print;