Question abount counting the total number of lines and put to an variable?

Hi..

I have a question about how to count the total of line that shows on
the screen. Here below is my code..

open (MYFILE, '123.txt');
while (<MYFILE>) {
if ($_ =~ /^User:/) {
print $_;
}
}
close (MYFILE);

then it will shows the following on the screen,

User: ABC
User: DEF

Is there any way that I can get the total of lines that show on the
screen and put to a variable? " Thank you..

.