#!/usr/bin/perl -w
# rename all files with a certain extention in a directory
use strict;
my $dirname;
$dirname = '/substitue_your_path_here';
opendir(DIR, $dirname) or die "Can't opendir $dirname: $!";
while ( defined (my $file = readdir DIR) ) {
# ignore current and parent directory . and ..
next if $file =~ /^\.\.?$/;
my $new = $file;
# substitute new file extension
$new =~ s/\.old_extension$/\.new_extension/;
rename($file,$new)
}
Reference Perl Cookbook Chapter 9 and Programming Perl Chapter 29