J:\johngg>i:\cygwin\bin\hexdump.exe -C test.txt
00000000  61 61 61 61 61 31 32 33  0d 0a                    |aaaaa123..|
0000000a

J:\johngg>perl -nle "next unless /^a+(.*)/; print qq{>$1<};" test.txt
>123<