use strict;
use warnings;

my @id = (' @itx.org ', 'tart@itx.com', 't_art@hotmail.com');

my @validid;
foreach(@id)
{
    my $valid = validate($_);
    if($valid)
    {
        push(@validid, $valid);
    }
    else
    {
        print "Invalid id $_\n";
        exit;
    }
}

print "Valid IDs: @validid\n";

sub validate
{
    my $id = shift;
    $id =~ s/\s+$//;
    $id =~ s/^\s+//;

    if($id =~ /^@|^\./)
    {
        return;
    }
    elsif($id =~ /^.*\@itx\.com/i)
    {
        if($id !~ /ca$/)
        {
            return "$id.ca" if($id =~ /com$/);
        }
        else
        {
            return "$id";
        }
    }
    elsif($id =~ /^.*\@\w+\.(?:com|org|net)/)
    {
        return "$id";
    }

    return;
}