use strict;
use warnings;

open OUT, '>', 'delme1.txt';
print OUT <<STR;
The use of the Porter and
 Ale is more prevalent in England. In the
United States ½ Old and ½ New Ale is usually used when this drink is
called for, unless otherwise specified.
STR
close OUT;

open IN, '<', 'delme1.txt';
my $str = do {local $/; <IN>};
close IN;

$str =~ s/½/&frac12;/g;

print $str;