I don't know how you can tell what is a "report" or what "last modified date" refers to. But you can use File::Find in Perl (sorry, not PERL) to find .shtml files that were modified in the last 30 days:

#! /usr/local/bin/perl -w
    eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
        if 0; #$running_under_some_shell
 
use strict;
use File::Find ();

# Traverse desired filesystems
File::Find::find({wanted => \&wanted}, '.');
exit;
 
sub wanted {
    my ($dev,$ino,$mode,$nlink,$uid,$gid);
 
    return unless /^.*\.shtml\z/s &&
    (($dev,$ino,$mode,$nlink,$uid,$gid) = lstat($_)) &&
    (int(-M _) < 30);

 # now do whatever you want with the file named
 # by $File::Find::name
 # this is probably not what you want to do:
 print("$File::Find::name\n");
}
[download]

This, by the way, was edited from the output of find2perl:

$ find2perl . -name "*.shtml" -mtime -30
[download]

update: changed unlink to print