なんか間違ってたので書き直した

@echo off
call :check_num %1 result
echo %result%
pause
goto :eof

:check_num
setlocal
if "%~1"=="" set "b=FALSE" & goto x
for /f "delims=-+0123456789 tokens=* eol=" %%i in ("%~1") do (
set "a=%%i"
if defined a (set "b=FALSE") else set "b=TRUE"
)
:x
endlocal & set "%2=%b%"