Is this what you mean?

[xorl@mybox]$ MYVAR = `myperlprog.pl`
[xorl@mybox]$ echo $MYVAR
stored output stored
[xorl@mybox]$
[download]

That's for the bash shell. Adjust as needed for other shells.

Is this really a perl question? Even I'm not sure what exactly you're trying to do and I'm usually good at guessing what people are actually asking.