directly from find2perl

#! /usr/bin/perl -w

use strict;
use File::Find ();

use vars qw/*name *dir *prune/;
*name   = *File::Find::name;
*dir    = *File::Find::dir;
*prune  = *File::Find::prune;

sub wanted;

File::Find::find({wanted => \&wanted}, '.');
exit;

sub wanted {
    my ($dev,$ino,$mode,$nlink,$uid,$gid);

    (($dev,$ino,$mode,$nlink,$uid,$gid) = lstat($_)) &&
    (int(-M _) >= 90) && unlink $name;
}
[download]

warning untested.
update: this example delete file older than 3 months, not within 3 months. just play with int(-M _)>= X AND int(-M _)<= Y for between time slice (X,Y in days).