Don't you get any more detailed error message than "mail not working"? (look in the syslog, MTA logfiles, etc.)

Anyhow, something like this works fine for me (my incarnation of sendmail needs the -t option to read the addressees from the message headers...):

#!/usr/bin/perl

open MAIL, "| /usr/sbin/sendmail -t" or die "$!";

print MAIL << 'EOF';
To: joe@here.com
From: smith@here.com
Subject: data subject
message body here
EOF

close MAIL or die "$!";
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