Here are some crude one-liners:

    perl -ne 'END{print"$v\t$k\n"while($k,$v)=each%h} $h{substr$_,0,5}
+++' file

    perl -ne 'END{printf"%7d %s\n",$h{$_},$_for keys%h} $h{substr$_,0,
+5}++' file

    perl -pe '$h{substr$_,0,5}++ }{ print"$h{$_}\t$_\n"for+keys%h' fil
+e
[download]

If you have GNU uniq then you can do the following:     sort file | uniq -w5 -c

However, the -w option isn't part of classical uniq.

--
John.