use strict;
use warnings;

my %sequences;

while (<>) {
	my $i = 1;

	for my $char ( split '', (split)[1] ) {
		$sequences{ $i++ }{$char}++;
	}
}

for my $pos ( sort { $a <=> $b } keys %sequences ) {
	my @charCount;

	while ( my ( $char, $count ) = each %{ $sequences{$pos} } ) {
		push @charCount, "$char:$count";
	}

	print "POS #$pos " . ( join ' | ', @charCount ) . "\n";
}

##</code><code>##

POS #1 a:4
POS #2 q:1 | b:3
POS #3 c:4
POS #4 x:1 | d:2 | z:1
POS #5 e:4
POS #6 f:4
POS #7 c:1 | a:1 | b:1 | d:1
POS #8 h:4
POS #9 i:4
POS #10 j:4

##</code><code>##

12 abcdefahij
12 abcdefbhij
12 aqcxefchij
12 abczefdhij