It isn't a fact. When you call something from the command line, the current working directory is where ever you are in the filesystem when you call it. Save this script to your home directory (say /home/me, to use your example):

#!/usr/bin/perl

print $ENV{PWD}, "\n";
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Then cd /home/me and ./testcwd. It will print

/home/me
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Then cd / and /home/me/testcwd. It will print

/
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