#!/usr/bin/perl
use File::Basename qw(fileparse);
@ARGV == 3;

my $dir = $ARGV[0];
my $old = $ARGV[1];
my $new = $ARGV[2];

opendir(my $path, $dir);
my @list = readdir($path);

foreach(@list){
        my $name = fileparse("$_", ".$old");
        rename("$name.$old", "$name.$new");
};