my $x = "chapter 5";
print "chap 5 ok!" if $x == 5;
# Throws Warning: Argument "chapter 5" isn't numeric in numeric eq (==)
$x =~ s/\D+//g; # eliminate all non 0-9 characters from string
print "chap 5 ok!" if $x == 5;
# chapter 5 is ok now!
# The string got "fixed" to be completely numeric
# Then when Perl made it into binary number to compare against 5, it worked!