how to shorten this code ? x occur how many times in variable

Can you please tell me how to shorten this?

my @an = split(//);
 my @num = grep { $_ eq ':' } @an ;

I was trying to see how many : occur in variable but didn't know how to 
do it fast so i did it like above...

I would like to see as many way different ways to get this done if possible

thank you!!


$var1 = root:x:123:/root:

trying to see how many times : occurs in $var1..... and I could only do 
it above way....