Not sure why yours isn't working, but is this what you're looking for?

#!/usr/bin/env perl
use warnings;
use strict;

my @bc;
my %count;
while (<DATA>) {
    my $BankCode = (split /\t/)[0];
    $count{$BankCode}++;
}

for (keys %count) { print "$_ $count{$_}\n" }

__DATA__
code1    fooz    barz
code2    fooz    barz
code1    fooz    barz
code3    fooz    barz
code1    fooz    barz
code1    fooz    barz
[download]

prints:

code3 1
code2 1
code1 4
[download]