Avoiding Spaghetti Code - batch-file

Question

I've been reading how to avoid spaghetti code in batch files.
In the example of what spaghetti code is, I realized that the batch file that I use when I logon almost fits this example. Could someone please help me make my batch file not have spaghetti code?
#ECHO OFF
CLS
:MENU
echo Welcome %USERNAME%
echo 1 - Start KeePass
echo 2 - Backup
echo 3 - FireFox
echo 4 - Exit
SET /P M=Please Enter Selection, then Press Enter:
IF %M%==1 GOTO StarKeePass
IF %M%==2 GOTO Backup
IF %M%==3 GOTO FireFox
IF %M%==4 GOTO :EOF
GOTO MENU
:StarKeePass
SET keePass="%USERPROFILE%\KeePass\KeePass-2.30\KeePass.exe"
SET kdb="%USERPROFILE%\KeePass\PasswordDatabase\PasswordDatabase.kdbx"
echo I'll start KeePass for You
START "" %keePass% %kdb%
GOTO MENU
:Backup
SET backup="%USERPROFILE%\backup.bat"
call %backup%
GOTO MENU
:FireFox
cd "C:\Program Files (x86)\Mozilla Firefox\"
start firefox.exe
GOTO MENU

Answer 1

In this case, if you want to use subroutines you should do this:
#ECHO OFF
CLS
:MENU
echo Welcome %USERNAME%
echo 1 - Start KeePass
echo 2 - Backup
echo 3 - FireFox
echo 4 - Exit
SET /P M=Please Enter Selection, then Press Enter:
IF %M%==1 CALL :StartKeePass
IF %M%==2 CALL :Backup
IF %M%==3 CALL :FireFox
IF %M%==4 GOTO :EOF
GOTO MENU
:StartKeePass
SET "keePass=%USERPROFILE%\KeePass\KeePass-2.30\KeePass.exe"
SET "kdb=%USERPROFILE%\KeePass\PasswordDatabase\PasswordDatabase.kdbx"
echo I'll start KeePass for You
START "" %keePass% %kdb%
GOTO :EOF
:Backup
SET "backup=%USERPROFILE%\backup.bat"
call %backup%
GOTO :EOF
:FireFox
cd "C:\Program Files (x86)\Mozilla Firefox\"
start firefox.exe
GOTO :EOF
Note that I changed a few things. Instead of goto... goto menu, you should use call :label goto :eof/ exit /b. Besides that, you had a spelling error StartKeePass, and instead of set variable="value", it's better to use set "variable=value". This will also accept spaces in the value, but it won't add quotes to your variable
Next time you should probably post this to code review, because these things aren't really errors

Answer 2

If you wanted to remove gotos altogether, you can simply call the script again to keep using it. Also, look into the choice command if you're using a version of Windows later than XP, since it will eliminate the need to check if the user entered invalid input.
#echo off
cls
echo Welcome %USERNAME%
echo 1 - Start KeePass
echo 2 - Backup
echo 3 - FireFox
echo 4 - Exit
choice /C:1234 /M "Please enter your selection: " /N
:: The first option listed by choice's /C option will return an errorlevel value of 1, the second 2, and so on
if %errorlevel% equ 1 (
SET keePass="%USERPROFILE%\KeePass\KeePass-2.30\KeePass.exe"
SET kdb="%USERPROFILE%\KeePass\PasswordDatabase\PasswordDatabase.kdbx"
echo I'll start KeePass for You
START "" %keePass% %kdb%
)
:: I've converted these to one-liners simply for personal preference.
:: You can keep these the way you had them if you put them inside of parentheses like with option 1.
if %errorlevel% equ 2 call "%USERPROFILE%\backup.bat"
if %errorlevel% equ 3 start "" "C:\Program Files (x86)\Mozilla Firefox\firefox.exe"
if %errorlevel% equ 4 exit /b
:: Calls this script again, simulating a goto :MENU
:: Personally, I'd stick with a label and a goto in this instance,
:: but this is how you could do it if you don't want to use goto at all
call %0
If each choice the user can make is fairly simple (i.e. it can be simplified to one or two commands), you might want to code this way; otherwise, definitely use subroutines like Dennis suggested.

Answer 3

My take on organizing this, added a reset to m variable, allowed some accidental input to be dealt with, and made it all checked in one block of code.
Nothing wrong with 'Dennis van Gils' answer, figured i would show you a different approach.
#echo off
setlocal enableDelayedExpansion
:menu
set "m="
cls
echo/Welcome !username!
echo/
echo/1 - Start keepass
echo/2 - Backup
echo/3 - Firefox
echo/4 - Exit
echo/
set /p "m=Please enter selection, then press enter:"
if not defined m (
cls
echo/Error: Empty input.
pause
) else (
if "!m!" equ "1" (
set "keepass=!userprofile!\keepass\keepass-2.30\keepass.exe"
set "kdb=!userprofile!\keepass\passworddatabase\passworddatabase.kdbx"
echo/I'll start keepass for you
start "" !keepass! !kdb!
) else (
if "!m!" equ "2" (
set "backup=!userprofile!\backup.bat"
call !backup!
) else (
if "!m!" equ "3" (
cd "c:\program files (x86)\mozilla firefox\"
start firefox.exe
) else (
if "!m!" equ "4" (
goto :eof
) else (
cls
echo/Error: ["!m!"] not recognized.
pause
)
)
)
)
)
goto :menu
Note: echo/ is used as a habit, as echo: and echo\ i mistake for parts of a file path/url, and echo. is so painstakingly noted for its longer command time.
Also, i prefer using ! over % along with setlocal enableDelayedExpansion by pure preference, and ease of block coding.