#!/usr/bin/perl -w


sub remplacer
{
    my $pos = index $_[0],$_[1];
    if ($pos != -1)
    {
	substr($_[0],$pos,length($_[1])) = $_[2];
    }
}


my $s = "Le chat mange";

remplacer($s,"chat","chien");
print "$s\n";

remplacer($s,"","Oui : ");
print "$s\n";

remplacer($s,"loup","chat");
print "$s\n";