bp_unflatten_seq: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/bp_unflatten_seq - from package: bioperl

You may install the required package with command apt-get install {package}

Error in other languages:
bp_unflatten_seq: bevel nie gevind nie
bp_unflatten_seq: comandă negăsită
bp_unflatten_seq: comando não encontrado
bp_unflatten_seq: commande introuvable
bp_unflatten_seq: command not found
bp_unflatten_seq: käsku ei ole
bp_unflatten_seq: không tìm thấy lệnh
bp_unflatten_seq: komanda nerasta
bp_unflatten_seq: Kommando nicht gefunden.
bp_unflatten_seq: kommandot finns inte
bp_unflatten_seq: komut yok
bp_unflatten_seq: nie znaleziono polecenia
bp_unflatten_seq: níor aimsíodh an t-ordú
bp_unflatten_seq: no se encontró la orden
bp_unflatten_seq: no s'ha trobat l'ordre
bp_unflatten_seq: opdracht niet gevonden
bp_unflatten_seq: parancs nem található
bp_unflatten_seq: perintah tidak ditemukan
bp_unflatten_seq: príkaz nenájdený
bp_unflatten_seq: příkaz nenalezen
bp_unflatten_seq: команда не найдена
bp_unflatten_seq: командата не е открита
bp_unflatten_seq: 命令找不到
bp_unflatten_seq: コマンドが見つかりません