# cat email_header.eml | ./parse_me.pl

##################
#!/usr/bin/perl
#
while (<STDIN>) {
    ..........
    $header .= $_;
    ..........
    # Passing $header as argument to sub
    &parse_header($header);
    ..........
}

sub parse_header {
    # How do I refer to the argument ($header)
    # passed to sub?  I want the whole contents
    # of ($header) to be passed.  Is it @_ or $_
    while (?????????)
    do this and that
}
##################