$string =~ s/find /replace/g;
$string =~ s/find /replace/gs;

##</code><code>##

open (FIN, "$inputfile") || die("Cannot read the input file");
local $/;
$string = <FIN>; 
close FIN;

$string =~ s/find /replace/g;

#and

$string =~ s/find /replace/gs;