Your terminal example corresponds to this:
perl -e 'print `bash -c "umask 0037 ; umask"`'

[download]
And it works as well. What you are trying to do corresponds rather to this terminal session: 
umask 0037
exit
umask

[download]
which, clearly, does not do what you want.

In reply to Re^3: invoking umask command in perl by choroba
in thread invoking umask command in perl by austin43

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