to_erl: 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 CentOS possible default full paths are:

/usr/bin/to_erl - from package: erlang-erts
/usr/lib64/erlang/bin/to_erl - from package: erlang-erts
/usr/lib64/erlang/erts-5.8.5/bin/to_erl - from package: erlang-erts

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/to_erl - from package: erlang-base-hipe
/usr/lib/erlang/bin/to_erl - from package: erlang-base-hipe
/usr/lib/erlang/erts-6.2/bin/to_erl - from package: erlang-base-hipe
/usr/bin/to_erl - from package: erlang-base
/usr/lib/erlang/bin/to_erl - from package: erlang-base
/usr/lib/erlang/erts-6.2/bin/to_erl - from package: erlang-base
/usr/lib/debug/usr/lib/erlang/bin/to_erl - from package: erlang-dbg
/usr/lib/debug/usr/lib/erlang/erts-6.2/bin/to_erl - from package: erlang-dbg

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

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