We usually pass a scalar to the chop() function, and usually it is a string. The function returns the last string character (or ASCII NUL, the backslash-zero character, if there is nothing to chop in the string) and it has the side effect of removing that last character from the string itself.
Here is a short example:
my $countdown = "0123456789";
my $current = chop($countdown);
last if(ord($current) == 0);
In an infinite loop we iteratively chop a string ouputting the chopped character. If the returned value from chop() is the NUL character we terminate the loop, otherwise we print it on a dedicated line.