ml-yacc.x86-linux: 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/lib/smlnj/bin/.heap/ml-yacc.x86-linux - from package: ml-yacc

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

Error in other languages:
ml-yacc.x86-linux: bevel nie gevind nie
ml-yacc.x86-linux: comandă negăsită
ml-yacc.x86-linux: comando não encontrado
ml-yacc.x86-linux: commande introuvable
ml-yacc.x86-linux: command not found
ml-yacc.x86-linux: käsku ei ole
ml-yacc.x86-linux: không tìm thấy lệnh
ml-yacc.x86-linux: komanda nerasta
ml-yacc.x86-linux: Kommando nicht gefunden.
ml-yacc.x86-linux: kommandot finns inte
ml-yacc.x86-linux: komut yok
ml-yacc.x86-linux: nie znaleziono polecenia
ml-yacc.x86-linux: níor aimsíodh an t-ordú
ml-yacc.x86-linux: no se encontró la orden
ml-yacc.x86-linux: no s'ha trobat l'ordre
ml-yacc.x86-linux: opdracht niet gevonden
ml-yacc.x86-linux: parancs nem található
ml-yacc.x86-linux: perintah tidak ditemukan
ml-yacc.x86-linux: príkaz nenájdený
ml-yacc.x86-linux: příkaz nenalezen
ml-yacc.x86-linux: команда не найдена
ml-yacc.x86-linux: командата не е открита
ml-yacc.x86-linux: 命令找不到
ml-yacc.x86-linux: コマンドが見つかりません