@lines = <>; #Slurp the whole thing.
$fh = shift @lines; #First line of whole is FH line
$ft = pop @lines; #Last line of while if FT line
chomp ($fh,$ft); #get rid of newlines
@segments = split /^BH/, join "",@lines; #split it up based on a BH at beginning of line;
shift @segments; #First segment will be empty.
foreach $segment (@segments) { #loop through segments
    $segment = "BH".$segment; #replace missing BH at beginning that was removed by split
    @lines = split /\n/,$segment; #split the segment on new lines
    chomp @lines; #get rid of newlines
    $batchhead = shift @lines; #first row is the Batch header
    foreach $trans (@lines) { #Loop through remaining
        process($trans, $batchhead); #process individual lines
    }
}