#!/usr/bin/perl
#
# renum.pl blah*.jpg
# blah1.jpg .. blah9.jpg blah10.jpg .. blah99.jpg blah100.jpg
# -> blah001.jpg .. blah010.jpg .. blah100.jpg

foreach ( @ARGV ) {
        next unless ($stem, $digits, $ext) = /(.*?)(\d+)\.([^\.]+)$/;
        $max = $len if ($len = length( $digits )) > $max;
        print "$_ $1\n";
}
$fmt = "$stem\%0${max}d.$ext";
foreach ( @ARGV ) {
        next unless ($stem, $digits, $ext) = /(.*?)(\d+)\.([^\.]+)$/;
        $new = sprintf $fmt, $digits;
        rename $_, $new or warn $!;
}