You can use the "exit" command as the last line of your PowerShell script. This will exit your PowerShell session.
You didn't say how you called the PowerShell script from Perl, but I suspect you called the powershell.exe binary.
Did you do anything like this ?
powershell.exe -File "C:\Scripts\myscript.ps1"
That should return when the script has finished (no reason to add an exit, that is there implictely at the end of the script).
You might try to add the NonInteractive parameter, but there should be no reason for that
powershell.exe -NonInteractive -File "C:\Scripts\myscript.ps1"
You can do
powershell.exe -help
to see the other available parameters
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