#!/usr/bin/perl -w

use strict;
use File::Find;

my $root_dir = '/temp';
my $new_shebang = '#!/usr/bin/local/perl';

find ( \&fix_shebang, $root_dir );

sub fix_shebang {
    return unless /\.(?:pl|cgi)/;
    local $/;
    open F, "+<$_" or die "Can't open $_: $!\n";
    my $file = <F>;
    if ($file =~ s/^#!.*perl(.*)\n/$new_shebang$1\n/) {
        seek F, 0, 0;
        truncate F, 0;
        print F $file;
        print "Found and modified: $File::Find::name\n";
    }
    else {
        print "Found (no modify):  $File::Find::name\n";
    }
    close F;
}