our ($rows, $cols);         #if use my ($rows,$cols), it will not work
no strict 'refs';                   # for ${$1}/g below
my $text;

($rows, $cols) = (24, 80);
$text = q(I am $rows high and $cols long);  # like single quotes!
$text =~ s/\$(\w+)/${$1}/g;
print $text;
#I am 24 high and 80 long