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@echo off
setlocal disableDelayedExpansion
echo.
echo * %~n0 { %1 }

set /a rearg1 = %1 - 1
if %rearg1% leq 0 goto :done

echo * before call :exec %0 %rearg1%
call :exec-fail %%0 rearg1
echo ..after call :exec %0 %rearg1%

:done
echo ..%~n0 %1 done
endlocal
goto :eof

:exec
call echo * begin :exec %%1 %%%~2%%
setlocal enableDelayedExpansion
set "exec=%1 !%~2!"
echo * before !exec!
!exec!
echo ..after %1 !%~2!
endlocal
echo * end :exec %1 !%~2!
goto :eof

:exec-fail
call echo * begin :exec2 %%1 %%%~2%%
setlocal enableDelayedExpansion
echo * before %1 !%~2!
%1 !%~2!
echo ..after %1 !%~2!
endlocal
echo * end :exec2 %1 !%~2!
goto :eof

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C:\>recurse 2

* recurse { 2 }
* before call :exec recurse 1
* begin :exec recurse 1
* before recurse 1

* recurse { 1 }
..recurse 1 done
..after call :exec recurse 1
..recurse 2 done

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C:\>recurse 2

* recurse { 2 }
* before call :exec recurse 1
* begin :exec2 recurse 1
* before recurse 1
* begin :exec2 !rearg1! %
* before 1
'1' is not recognized as an internal or external command,
operable program or batch file.
..after 1
* end :exec2 1
..after call :exec recurse 1
..recurse 2 done

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* before recurse 1
* begin :exec2 !rearg1! %

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@echo off
setlocal disableDelayedExpansion
set var=value
cls
echo before direct
call :direct
echo after direct  var=!var!
echo(

echo before direct2
call :direct2
echo after direct2  var=!var!
echo(

echo before indirect
call :indirect
echo after indirect  var=!var!
exit /b

:indirect
setlocal enableDelayedExpansion
set cmd=part2
echo begin indirect  var=!var!
!cmd! arg1
echo end indirect NEVER REACHED
exit /b

:direct
setlocal enableDelayedExpansion
echo begin direct  var=!var!
part2 arg1
echo end direct NEVER REACHED
exit /b

:direct2
setlocal enableDelayedExpansion
echo begin direct2  var=!var!
part2 arg1
echo end direct2 NEVER REACHED
exit /b

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@echo off
echo part2 main      var=!var!  %%1=%1
exit /b

:indirect
echo part2 indirect  var=!var!  %%1=%1
exit /b

:direct
echo part2 direct  var=!var!  %%1=%1
exit /b

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before direct
begin direct  var=value
part2 direct  var=value  %1=arg1
after direct  var=!var!

before direct2
begin direct2  var=value
The system cannot find the batch label specified - direct2
after direct2  var=!var!

before indirect
begin indirect  var=value
part2 main      var=value  %1=arg1
after indirect  var=!var!

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set x=%~1
call :mathlib.multiply %x% 2 x
call :mathlib.increment %x% x
echo 2 * %~1 + 1 = %x%
goto :eof

@rem the following assumes that mathlib.cmd exists and has
@rem :mathlib.multiply, :mathlib.increment labels which do the obvious
:mathlib.multiply
:mathlib.increment
mathlib %*
echo this line NEVER reached
goto :eof

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@echo off

call :testLabel
echo part1 end
exit /b

:testLabel
echo part1 testlabel %%0 = %0
part2 argFromPart1
echo Never reached
exit /b

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@echo off

echo %0 main
exit /b

:testLabel
echo part2:testLabel %%0=%0 %%1=%1
exit /b

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echo hello & part2 ...
verify >nul & part2 ...
(part2 ...)

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(
  part2 ...
)