Without a code example it's hard to know why it's working the way it is instead of the way you want.

Try using backticks and assigning the results to a variable; i.e.:

my $passwd = `cat /etc/passwd`;
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Note that those are backticks (`) which share the same key as the tilde (~)(at least on my keyboard, but I'm not a Mac user, so YMMV), not single quotes (').