Look at your spacing and what you are using for the qw delimiters.

My code uses qw$$ while yours uses qw().

Try these:

perl -e 'my $rev = (qw$Revision: 1.41 $)[-1]; print $rev, "\n"'
perl -e 'my $rev = (qw($Revision: 1.41 $))[-1]; print $rev, "\n"'
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